I'm an atheist and although I've never been on a Beliefs thread at all, I can't see how you can possibly think that non-believers have less right to / reason for posting on there.
Absence of belief in something doesn't equate to absence of opinion about it. There's not a person in the world who doesn't have an opinion on religious belief, just as everyone has an opinion on, say, the death penalty, democracy, ghosts, extra terrestrial life or any other abstract concept.
On that point, despite the impression given by the extreme favour (ie legal protection) granted to religion-derived opinions in most societies, there's no logical reason why non-religious personal beliefs deserve any less accomodation. Ultimately, it's all just stuff a person happens to think. How come it gets more weight when a book that sort of vaguely backs some of it up? Why not the same protection for vegetarians, say (I'm not one, btw). It's to prove exactly this point that all those people put Jedi on the census. If enough other people all think something, that something is deserving of as much respect and allowances as any 'religious' belief, legally and morally.
It's convenient isn't it? I'm not supposed to upset believers by disagreeing with them, I'm supposed to leave them alone in their little belief bubble, but yet they seem to feel quite free to invade my world through the media, ads etc to disagree with my opinions about, say abortion, or homosexuality. Not to mention the parliamentary lobbying all over the world to try to practically influence EVERYONE's world in respect of abortion, contraception etc.
So yeah, in light of all that, I think if I wanted to come on a belief thread and tell people I think they'd got it all wrong I'd be perfectly entitled to.