I don't think the evil nature of the spell is too much of a problem. It should add conflict to the party for sure - the Paladin should oppose evil acts. Habitual, unrepentant use of evil necromancy may eventually drive a wedge between the characters and split the party.
More immediately, the paladin may feel obligated to seek legal recourse on behalf of the disturbed dead. Desecration of a corpse and slavery may be against the law. The paladin may need to bring the wizard to justice.
Evil necromancy could be lawful. If the paladin is high-enough level, he could just turn undead to destroy anything the wizard tries to animate. "I won't abide evil necromancy, so don't even try!" Assuming doing so isn't considered destruction of property. If the meat shield is busy undermining what the wizard does instead of hacking at enemies with that +5 holy avenger, the bad guys have more chances to hurt the fragile wizard.
The context of the spell could temper the paladin's response. Animating your slain henchmen to haul loot from the dungeon crawl two weeks back to town is not the same as animating the slain donkeys to do the same. Animating dead henchmen before combat to eventually serve as meat shields is not the same as animating slain enemies during combat to win the day and banishing them afterwards.
I don't have AD&D 1st edition rules handy, but the OD&D Rules Cyclopedia says "Lawful clerics must take care to use this spell only for good purpose. Animating the dead is usually a Chaotic act." If lawful clerics can use it for good, paladins should be no different.
Gail Z Martin has a good necromancer in The Summoner and other Chronicles of the Necromancer books. Aragorn uses the dead men of Dunharrow against Sauron's allies in The Return of the King. Other literary examples escape me for the moment.
The question is a bit unclear and I’m not quite ready to delete my other answer since I’m not sure it’s inappropriate, but I think this would get lost in it and may be closer to what Zach wants, based on comments.
Therefore, I am answering two questions here:
How should I tell a player that he’s not playing a character the way he should be played?
How should I deal with a player who describes his character as one thing, but plays him as something else?
I separate these two because they are different question, and need different answers.
1. How should I tell a player that he’s not playing a character the way he should be played?
Simple: you don’t. That’s none of your business. If a Paladin needs to Fall because of his actions, then that’s what happens (but see my other answer for thoughts on how best to handle that mechanically – I despise the official rules on the matter, and never recommend them), but it’s because he’s not being a Paladin, not because he’s not playing how you imagine the character. It’s his character, not yours.
In effect, when you ask how to do this without seeming to accuse him of bad roleplaying and/or trying to play his character, the answer is you can’t, because that is exactly what you would be doing. Maybe he is roleplaying badly; maybe that accusation isn’t unfounded, and maybe that’s a discussion you actually should have. But if he’s not roleplaying “badly,” there shouldn’t be any need to comment at all.
2. How should I deal with a player who describes his character as one thing, but plays him as something else?
This is a different matter. Particularly when the character’s backstory touches on the rest of the world, as your player’s does with his father as the head of an order of paladins, there is a greater cause for concern and a greater need to set things straight. Remember, while his character is his, the setting is yours. If your setting does not include any order of paladins that would condone or accept his behavior, then he can’t be a member of one – or he is about to get into trouble with them.
And if he was raised to be this way his entire life, and up until now upheld those standards, maybe they’re going to worry if he’s been cursed or possessed or something. But maybe he hasn’t been – maybe he felt stifled in the order, and now that he’s out in the real world he’s feeling a bit restless and rebellious. Maybe he’s looking for a bit of independence from a father in whose shadow he’d spent his entire life, whatever.
But the key thing is for the player to recognize that his actions do not jive with his backstory. I suggest that you give him these choices:
Change how you behave, to be more in line with how the character was described in the backstory.
Change your backstory, to make your character a bit more rebellious or a bit more light-hearted; maybe his father hoped that going out into the real world would make him a bit more serious.
Keep both the behavior and the backstory, and accept that this is very much an abrupt change in his behavior. Tell him that the order will not be amused, and will be greatly concerned about it, possibly even angry.
All of these things, however, have more to do with the order’s rules, and not the Paladin’s Code of Conduct. In both the second and third case, however, warn him that Falling is a very real concern for the order. They do not appreciate his behavior precisely because they believe it will cause him to Fall – and point out that putting others in danger needlessly is something that could cause him to Fall quickly.
But like I said in my other answer: a Paladin’s allowed to have a little, or even a lot, of harmless fun, so long as it is harmless, and he remains that unwavering bastion of Good and honor. Throwing a chair at someone or throwing an ally into a group of enemies may not be harmless, but there certainly are plenty of “un-Paladin-y” things he could do (e.g. harmless pranks) that will never cause a Fall.
Best Answer
The biggest issue with paladins is when their partners' behavior is judged as if the paladin himself had done the deed. If your DM is willing to avoid that pitfall, may I suggest...
A paladin who does not expect non-believers to obey the laws of his faith. He hopes that through his shining example his teammates will come to see the value of his code, but believes that doing Good under threat of punishment doesn't count. He guides the party to consider mercy, but does not expect them to follow oaths they did not swear. Perhaps his own past is not lily-white and he recognizes that true Faith takes time; he is patient with the party.
Underen commented: When the PCs ignores the paladins advice, simply tell them in character: "Remember, the gods will be the judges of your actions. I wash my hands of this.
It's important to recognize that the values of D&D are not our modern values. Justice is often swift and brutal when you don't have the luxury of modern civilization. Think wild west justice or battlefield trials. As a paladin, you might have the authority to conduct hasty trials; ask your DM to consider this1. Remember there are methods of punishment that fall between letting criminals go unpunished and killing them: from taking their stuff, to branding or even cutting off a finger or a hand2, there are a spectrum of options.
Just as you are considering the enjoyment of your friends at the table, the DM and other players should be willing to meet you half-way. The player characters should do the same for their friend the paladin. This is a mutual storytelling challenge: a group of friends (or at least comrades-in-arms) with different moral attitudes is pretty common in real life and in storytelling. How do they function without coming to blows? That's a cool story for your group to tell.
Making the Tough Decisions is an essay by Rich Burlew which addresses (in more general terms) the exact problem you're facing.
1 There can be some confusion about the paladin's requirement to "respect legitimate authority," and whether one's class dictates in-game social duty or privilege. As I understand it, 'Paladin,' 'Cleric,' and all other class titles are meta-mechanical terms rather than in-game titles/distinctions unless you're in a setting that makes it explicit. Thus no character (player or non-player) has legitimate authority by virtue of their class alone (there are some rare PrC exceptions to this, whose explicit nature supports my general claim). Authority is conferred based on merit, heritage, experience (and possibly bribery). My suggestion that your paladin might have some legitimate authority is explicitly at the whim of the DM. It could just as easily be bestowed on a bard or a fighter, should social circumstances warrant it, and serve the same purpose --perhaps even better.
2Perhaps I should clarify that branding and mutilation in these contexts are not about sadism: they are about preventing future crime without killing the criminal, in a land without good jails. Brands alert future targets that they are dealing with a particular kind of criminal, and cutting off a gun-happy outlaw's trigger finger makes it harder for him to kill.