And then, once more, it has to be a terrible crime ? The players don't even try to understand why it was done, they just slam the door, walk away and use the DM as a "bad DM" example until the end of their days ?
I have a different take on this, which is that there was a REASON for which the DM did what he did. But honestly, people in here are much too self-righteous and theoretical to ask WHY the DM did it. Because in my experience, it's because he looked for another solution to try and please the players and did not find one. So does it make such a terrible crime ?
Ok, let's dive down a little deeper here.
I know exactly why the DM that I had railroaded us. Back in a 2e game, she was running Keep on the Borderlands. We were playing away and then had the idea to rob the jewel merchant. Spent an entire session planning, working it around, scouting, the works. We were going to go on A HEIST! The entire group was involved. Then, when it came time to execute our cunning plan, she declared that the night before, the jewel merchant, without any prior notice, had closed shop and left in the night never to be seen again.
Now, I know why she did this. She didn't want us to do this. She had seen her campaign go off in a completely different direction and had decided to get things back in the "right" way again. I know this because she told me so afterward.
We still immediately quit the game.
Again, this gets back to my contention that the purpose of a GM is to run a game that the players enjoy. If the players are right into something, completely focused on it, playing the game and having a blast, and the DM then plonks down a big "THOU SHALT NOT" sign, well, that's bad faith. Had she told us about this before we spent several hours of game time planning and whatnot, then it probably would have been okay. But, she made a mistake, didn't step in when she should have and then stepped in in the worst possible way - total railroad.
And, to make matters worse, she insisted that she did nothing wrong. She did not see why we were unhappy. So, we walked.
In other games where I've seen this sort of thing rear its head, it's generally always been the same thing. The DM wants to enforce a specific outcome because the DM has decided that that specific outcome, come hell or high water, is the "best" for the enjoyment of the table, irregardless of the perspectives of the players. It's the NPC who will refuse to give out information because that will make things "too easy". ((So, the players bypass this by resorting to magic, and, next time, the NPC will be impervious to charming - then the DM pisses and moans that the players never talk to NPC's)) It's automatic roadblocks the pop up to "make things more difficult" which instead mean that the players never try anything that isn't specifically called out by the mechanics. ((resulting in DM's bitching about how their players just aren't creative anymore)) So on and so forth.