I'm currently in a campaign run by a friend, and so far, I'm having a great time. However, he does do one thing that has been irritating to me, he makes all of the important allied NPCs far more powerful than our party. Now, I get that some NPCs will be more powerful than us, but when every single one is able to crush a party member without a second thought — and does, when we disagree — it's starting to feel a bit railroady. How am I supposed to deal with this DM, as I want to continue playing, but I'm tired of having my life threatened by everything I meet?
To clarify, the overpowered NPCs are not villains, they are allies. The villains are beatable, but it's our allies who are too powerful.
For Example: We found a changling spy among us, and eventually knocked him out, which the DM did not expect. We decided to keep him for questioning, but suddenly, an ally of ours, a magical-rogue NPC, who has been stalking us shows up and attempts to drag the changling away to have it killed. I attempted to stop him, arguing that it could lead us to its master, but the NPC merely used his power to knock me out in one shot.
For another example, we needed to save a girl from a fortress, but lacked the equipment. The (same) rogue suggested we uses a guarded back door and merely fight off the guards, but we decided to go in from the underground and planned around that, but the rogue forced us to take his suggestion.
This rogue is just one example, but he is often used as an intervention wedge between us the players and our goals. The DM follows the rules, but the NPCs are often so powerful that its indistinguishable from DM fiat — he decided they were that powerful after all.
Best Answer
The only real thing you can do is talk to your DM. Explain to him why you dislike his way of playing. The only way to get him to change this behavior is to talk to him AND show him a better way. I know this probably isn't the answer you're looking for but sadly it's the only thing you can do.
Furthermore, realise that DMing without railroading tends to be difficult even for experienced DMs. A lot of DMs don't like to see all their preperation go to waste because players went in a totally different direction than the DM anticipated. An experienced DM can usually better predict what players are going to do and are better at thinking on the fly. If he is inexperienced, give him tips, tell him what he did well and what he could have done better.
Another thing you could try is DMing a few sessions yourself in which said DM will be a player. If anything you'll get to understand each other better.
Lastly, just in case it is relevant. If you're playing a prewritten campaign, your DM might have issues with unanticipated results because the module will probably not instruct him on how to react. If that's the case, he just has an extra incentive to railroad you.