I'm so tired of the "you don't understand what I believe therefore your argument is invalid" cop out. It's total BS. My favorite quote from the article (bolding mine):
We also have to be willing to accommodate the fact that belief comes in infinite shades and varieties. No two people believe exactly the same thing, and that presents another opportunity for evasion: plausible denial that you believe what is being attributed to you. We have to accept that, to make progress, we sometimes have to say, "that's not quite what I think, but it may be close enough. Go on." If anything less than perfect understanding counts as misunderstanding, then everything is misunderstood.
I see this all too often. Any comment that doesn't address the exact nuance of a person's belief is completely discarded as invalid. I can't decide if that objection a bigger piece of BS than the original belief or not.