My response to this, in discussions in DND and beyond (even into work and non-gaming social situations), is simple. If Bob has interrupted Alice:
Bob, Alice was speaking.
Or, if Bob has interrupted me:
Bob, I was speaking.
Raise your voice (admittedly, it's easy for me, because I'm a very loud person), and put on your best firm teacher and/or mom voice. When a GM doesn't manage a session enough to stop this, sometimes you have to pipe up and put your foot down. The tone is key, here. You don't want to sound either angry or whiny, because if the attention hog is actually malicious, they will likely turn that on you. A firm voice and a neutral, but accurate, statement normally does the trick for me.
If you are worried about being overly harsh or too authoritative, qualifiers work wonderfully:
Hey, Bob, I think Alice was speaking?
while still getting the point across.
Say No - say it early, and say it often with this group. Talk to them about it.
Even though I highly discourage railroading sometimes "No" is the appropriate answer. A lot of DMs are afraid to say no because they are worried the players will feel raidroaded. This can create a lot of problems like the ones you listed above.
If you are starting a new campaign take a look at the characters the players have created. If you want don't allow neutral or evil alignments. Don't allow characters who are murder hobos. I'm not saying require all lawful good paladins, but don't allow the types of characters that won't move the campaign forward. Start saying no at Session 0. Set that expectation.
Before every campaign/every new character creation my players send me their back stories. I have said no to certain things many times (usually to Chaotic Evil alignments or murder hobos), and no one has pushed back hard against it. On the "say it often" players can attempt to rob a store/overthrow a government. But when a player consistently tries to harm every NPC and the in game consequences don't change anything a no is necessary. Often.
I have a feeling in game punishments won't work (i.e. when they set fire to the Queen the lvl 20 fighters in the room attack the party and kill them). In this case, you're going to need to meta and say "No." The players probably won't like it, but the line has to be drawn somewhere.
Don't be afraid to bring it up. Let them know they're making it hard and unenjoyable for you. If they are people who are worth playing with they will change their playstyle for you. If they don't, then let them know the group just isn't for you. Most players are understanding. I've never had an issue that I've addressed that has been ignored (but normally I am host and DM, so I have a lot of "clout"). Still, if your players are good humans they'll be understanding.
There was one guy who went to find another group when I wouldn't let him attack a child for "RP" reasons. Before every campaign/every new character creation my players send me their back stories. I have said no to certain things many times (usually to Chaotic Evil alignments or murder hobos), and no one has pushed back hard against it. On the "say it often" players can attempt to rob a store/overthrow a government. But when a player consistently tries to harm every NPC and the in game consequences don't change anything a no in necessary. Often
As far as "Tom" goes... some people forget D&D is just a game. As you said, with him being the host things are more difficult. But if it creates such a problem then look into another place to play. I know finding someone to host can be difficult, but it might be worth the effort in this case.
Best Answer
Explain it to them just as you explained it to us:
"It makes me uncomfortable and I believe it will make the other players uncomfortable." is a perfectly valid reason to veto a character.
It also may be worth telling them to prepare another character "just in case" and bring up their character concept in session zero, the other players may be OK with it, exploring things in a game that would not be acceptable in the real world can often be fun depending on how the player handles it. You can say "If the other players are OK with it I will allow it for not but if you push it too far and it makes anyone (including you) uncomfortable then the character leaves and you bring in your spare, no questions asked".
Other players may be fine with it, this may be affected by how "real" they play the bigotry and how real the setting is, a Caricature can be fun. I myself had a lot of fun playing a racist (clade-ist?) lizardfolk who just did not like mammals "You all have things hanging off you", (genitalia, breasts, hair) "and you're always leaking fluids, it's just weird.". He still saved the world with a group of mammals and the other players had fun with it as well, especially because he was fine killing (and eating) mammalian humanoids but went to extraordinary lengths to not harm intelligent reptilian enemies. The fact he was a bit monstrous (seriously he ate like a dozen people throughout the campaign) made it more fun and unreal enough to not be uncomfortable. But I also talked it over with all the other players at session zero to make sure they were fine with it beforehand; these were players who knew me and knew I was just playing a monster.