Okay, dude, stop for a second. Your statement seems to lack appropriate perspective. It seems to me that you're telling me that having a calm discussion at a gaming table (a discussion which, as several have already pointed out, is not necessarily about wheedling around a, "No") is equivalent to a threat to all of society.
No, it isn't. And here, no means no.
let us not be hyperbolic. You're a GM, not a cop at a crisis scene. Asking you a simple question is not going to cost human life or something. It may leave some folks cooling their heels for a moment or two while the question gets answered, or the GM tells the player to take a hike. And that is about it.
Real people have this thing called judgment, which allows (most of) them to differentiate between different social contexts. Just because they ask a question at your table does not imply that they never take no for an answer.
If you think for one moment that signs found in gaming are not related to other parts of life, then YOU are the one needing to gain perspective.
Someone showing signs of a threat to the game itself, is not someone going to be welcome to games I run.
You are sadly still working inside the vacuum, think that the DM and player are only in existence in the case of the DM and player in so much as the player left everything of there life out of it, and humans don't work that way.
You may want to learn a bit about psychology and things called behavioral patterns. One exhibiting such a pattern from the onset of gaming, is not likely to change, ESPECIALLY if they exhibit those in the rest of their life. I don't have interest in finding out or risking my players in in manner, not limited to the fun of the game, for such people exhibiting those patterns.
I could illustrate this very well using your position on the forums, where you already DO, if that is your tasked position, do that pattern recognition and prevent "harm" to the enjoyment of others. Unless I misunderstand the position of the green names here.
The job is the same as a DM. It only takes ONE time for a person on these forums to get threadbanned for threadcrapping even if that is there first post, correct?
Well that is what I am doing as a DM, when I remove the element that comes to the "no tieflings" game with the intent of bringing tieflings into it.
Some may say, not openly as it violates the forums rules, that certain instances of your actions in your duty were unwarranted, and likewise mine as a DM. I will not change my DMing to placate those who do not agree with it, and likewise I don't assume you in your forums position would change just on the whim of another either.
The tasks are very similar. Based on your personal perspective, you do what you feel is right for the protection of the larger group, and so do I.