I don't think it's fair (or even the way the voting thing is supposed to be used - I could be wrong about that), if people just don't like the subject (or don't agree with/believe in the subject), but it's presented in an objective way (as if the author acknowledges that there are other lines of thinking related to the subject. I realize now that what I'm trying to say is more difficult than I immediately thought (maybe because it's 7:00 a.m. Sunday morning and I haven't had enough coffee yet lol). Anyway, an extreme (and make-believe) example might be a Hub that says that Elvis is alive and well and living in Florida. It's one thing for the author to (essentially) say, "This is what I believe and why," (I don't think that should be voted down), or "This is what a lot of people believe and why" or else "This is why there's a movement to prove that E. is alive and in Florida". I don't think either of those should voted down because they're informative and objective. I think, though, if the author does something along the lines calling the Hub, "Where is Elvis now?" and presents that as if it's indisputable/undisputed fact.
I suppose my measure is whether I know for a fact that what the author presents can be/has been proven wrong by experts and research and (ideally) first-hand observation. Even then, though, I think people have to consider whether it's one isolated fact they disagree with/don't believe or whether it's a whole subjects-worth of ideas. If it's an isolated fact I think people should a) comment and say that disagree and/or ask the author if he can back up the fact somehow; or maybe (if they want to be bothered) e.mail the author, state why they dispute the fact, and suggest the author double-check and maybe clarify or correct anything that needs it. I don't think one or two things should necessarily get voted down without someone's giving the author the chance to clarify/back up.
If the whole Hub is about something that "legitimate" resources/experts are divided on, then that much should be included unless the author knows, for a well established fact, that the experts on one side are right while the others are (as the author has seen/experienced for himself and has backed up by enough of the well respected experts/resources in the field on his side). So basically, before someone votes down he ought to first consider how well he can back up his own side to things (beyond just his opinion and a few experts who might back it up).