I think "shooter down of new ideas" is getting unfairly lumped in with those other actually-bad traits. If there's one thing a lot of "idea guys" and optimistic entrepreneurs tend to lack and need, it's a skeptical partner who keeps them grounded in reality. Someone who is experienced, seen it all, constructively critical. Someone who will say "Wait a minute, this was tried in the '80s, and it won't work. Maybe try this instead." If you lump "people who push-back" in with haters and trolls, you're going to end up surrounded by yes-men.

The tech landscape is littered with failed projects that could have been stopped early if the idea person had a sounding board that keep him/her realistic.