As they say, there are two rules in improv: Never say no, and never ask why. When another actor asks 'Why?' or says no to something you're suggesting, then it's very clear that they're putting the onus on you, because they're not comfortable with it themselves.
“With two thousand years of Christianity behind him... a man can't see a regiment of soldiers march past without going off the deep end. It starts off far too many ideas in his head.”