I don't think this is quite right. Clearly some of them think that high level human fighters can be run through many times by swords and not die, even though the rules for AD&D state the exact opposite.
And many seem to think that a giant can literally hit a person with a club yet that person not be knocked down.
I don't think the strong views are about what ordinary people can do. I think they are strong views about game conventions - as we have seen in this thread, such as the convention that a fireball must damage everyone in its AoE, or that a person who is attacked by a sword-wielding warrior must have a chance of taking no damage at all.
But, you're still getting hung up on the why. Why do people take this position? It doesn't really matter. The only point of asking why is to try to convince someone that their position is wrong.
And the past ten or fifteen years have proven one thing beyond a shadow of a doubt, you can't convince someone that their position is wrong. What you see as inconsistencies are bound by that interpretation. The GAME DEFINES this. Giants cannot knock someone down because the game says so. And if you believe that the game itself defines reality, then, there is no inconsistency. A human fighter can be run through multiple times because the game says that that's okay.
The whole issue here is you are trying to define in game events separate from the mechanics. Those that disagree with you will never do that. In game events are DEFINED by the game itself. Thus a fireball is never avoidable, but, a giant cannot knock someone over. When they talk about "simulation" that's what they're talking about. That the game world is defined by the rules of the game. And, those rules have been, more or less, static from OD&D to 3e. When 4e came along, many times the powers didn't actually define anything about how something happened. You use the power, this happens, but, any narrative is supplied by the players, not the system. So, your Biting Assault doesn't really work because how do you pound something with a light blade or a crossbow? Crossbow only shoots once. That's what the game says it does.
Now, for you or me, this isn't a problem at all. I get that. I agree with you. But, they will not ever agree with you here. It doesn't matter how many examples you bring up, how many quotes you point to, how much evidence you bring. It does not matter. You cannot win this argument. It's not possible. They are starting from a position that is fundamentally different from yours or mine. Humans can't jump 30 feet because the tradition of the game says that they can't. Fireballs always hit because the tradition of the game says that they do. Weapons MUST have a chance of failure because tradition says they do.
Which is why they reject so much of 4e. 5e gets away with it because they made just enough nods to those traditions that the changes that were made became acceptable. So, ten years ago, in D&D Next, if you tried to add in damage on a miss, it wouldn't be possible. People would have lost their minds. Now? Now it gets through because there is enough tradition for the idea to slide past.
Rules and games can be judged by their traditions. It may not be how you or I do it, but, it can be done that way.