on a discussion board? no, there is no onus of proof, because nothing is riding on it, just as you don't need proof to reject the ideas.

demanding citations is the favorite trick of people who want to waste your time precisely because they disagree with you and no matter what you come up with, they'll never give in. therefore, one should never give in to it.

rather, doing your own research and contributing it to the discussion is the lifeblood of online communities.