If I'm saying why I shouldn't join, either of "I haven't the time" or silence is fine. If I want to say why you shouldn't join, we should set the bar high, so that if I use joining as a cheap shot against you I look bad. "You joined a website with a stupid font" is what people fear, and so that might be what we need to act against.

Incidentally, what timezone are you in and when do you sleep? I'm always a bit surprised to get responses from you in the morning...