Oh dear, calm down.
Poster A's idea may have merit, but that doesn't necessarily mean that Poster B also thinks it has merit. The issue you seem to be addressing is that Poster B should at least hear out Poster A before coming to a conclusion to A's idea. I think that is a good thing.
The problem occurs when Poster A's idea is unpopular or on the fringe. Poster B then sees no reason to engage the idea because the contradiction is self-evident. Here is an example:
Poster A: The Holocaust did not happen the way the history book claims. The number six million came about to demonize the NAZIs and isn't accurate to what the real numbers where, which is considerably less. Let's debate.
Poster B: I refuse to debate this because you are self-evidently wrong.
Now that is extreme, but I wanted to be 100% clear in my example. There are opinions that will automatically be disregarded. Racial superiority is another example.
Another example, less extreme, is this:
Poster A: I think there is a problem here with opinions being stifled.
Poster B: I don't see it.
Poster A: It is there.
Poster B: Show me.
Poster A: How can you not see it?
And so forth.
In this example, like any debate, a real might exist or it may be in Poster A's mind. Poster A has the burden of proving the claim of stifled opinions. Poster B should listen without showing contempt for A's opinion.
If Poster A thinks his or her ideas are being pigeon-holed, then Poster A should re-think his or her approach to the subject. A strong post with solid claims will be harder to pigeon-hole. Because A is making the claim, it is his or her burden to adequately prove that an injustice is happening or that his or her opinion is more correct. That's how debate works. Sometimes an opinion doesn't gain ground, and this can be for a variety of reasons, but the proponent should have the fortitude to re-tool his or her idea, or back off until another time arises.
Is that what you were looking for, hal?