Not sure about your third point. It seems like he's genuinely echoing a point that's been made many times before: that good ideas can sound stupid at first. http://paulgraham.com/ideas.html
I don't think he's trying to show any superiority by telling us the details of how his conversations went about.
But I'm not sure about the merit of the position that expressing a strong opinion early on is a form of arrogance. If 90% of the time stupid ideas (as well as good ideas) simply don't pan out, then perhaps one can say that an opinion that something is "stupid" is not only unarrogant, but accurate. Then again, my point is that calling something stupid or smart really is largely irrelevant because the odds of success / failure are the same for ideas that are equally stupid and great. I'd like to see a post on the arrogance of calling something Great when it truly is not. That sort of hubris exists in equal quantities in the VC world.
I agree that one should give all ideas the possibility of success. But it's just human nature to judge things as stupid or smart. And as the animals that we are, our opinions largely don't matter in the grand scheme of the universe. Arrogant or not.
I don't think he's trying to show any superiority by telling us the details of how his conversations went about.