Great topic. I see some gents prefer the honest approach. I think ignoring someone is unprofessional, so I try to keep it simple and say, I don't think we'd be a good fit. Which is the truth, just maybe not the whole truth.
Sometimes when getting a reference, a reputable lady tells you something or you find something out through a verification site or see a post here that makes you think, hmmm I'll pass. I know there have been a few times that a gent messages me through p411 and after looking at his OKs, I'll say I don't think we'd be a good fit.
How could I possibly tell someone, "well after looking at your posting history, you seem like a card carrying incel or a douche" in a polite way? I don't want to hurt anyone's feelings and I hate giving an exact reason for fear it could create drama, especially if the issue at hand was told to me in confidence.