PZ Myers and Hemant Mehta are pushing for an atheist "Unity Convention". Good for them, I suppose, but I personally don't think it's all that great an idea. More importantly, I wouldn't attend such a conference, and if I were a member of an atheist organization, I wouldn't vote to subsume our group's yearly convention for a unity convention.
First, I personally am well and deservedly despised by many in the atheist community. There are a lot of atheists who don't just disagree with me, who don't just think I'm a giant asshole, but consider me a disgrace not only to atheism but to humanity in general. I'm not complaining — the feeling is more-or-less mutual — but why would I want to hang out for a whole weekend with people who actively and passionately hate me? And why would they want to hang out with me?
Atheists as a whole do not have any shared interests, only a very broad and statistically vague disbelief in a personal god. Even naturalist atheists as a whole have no shared interests, only a somewhat narrower and more precise epistemic privilege for science... and there are already plenty of scientific conferences.
There's not just a lack of shared interests, but a lot of mutual contempt. The "appeasers" don't just disagree with the "shit-disturbers", they despise them. (I can't think of anything more nauseating than PZ Myers cuddling up with Chris Mooney.) The atheist communists despise the atheists Randians, and vice-versa, likewise with the skeptical atheists and the woo-woo Buddhists.
A "Unity Convention" would simply see members of the various atheist groups hanging out with each other, with a little bit of worthless ecumenical tokenism. At worst such a convention will be full of very heated controversy — which would seem to defeat the purpose of a convention specifically designed to show our unity — at "best" it would devolve to the lowest common denominator, an endless repetition of, "Do you believe in god? No? Great! Me neither!" Yeah, good times.
There's nothing wrong with these deep conflicts, conflicts that go past disagreement into real enmity. Atheism is not a moral or ethical position, and there's no objective truth to any moral or ethical position. Substantive ethical differences are not the same as disagreements about scientific truth; there's a degree of ethical difference where there's no appropriate response other than enmity. The Randians and Communists, for example, both believe the other promotes bullshit propaganda to literally enslave humanity; they are agreed only that god talk is an inappropriate way to do so.
(Keep in mind that enmity does not mean violence. The accommodationists and the confrontationalists despise each other, but they don't want to kill each other, and there's no reason to believe they would. Enmity is different too from factionalism: enmity arises from substantive ethical differences; factionalism from blind loyalty. Enmity only superficially resembles factionalism in that both tend to create emotions of hostility. And even factionalism usually represents an underlying substantive ethical/political division; even in factions within a religion, the differences in apparently meaningless scriptural interpretations follows from a more substantive ethical difference.)
If the goal is just to get as many atheists together to just stand in the same place, then it would seem easier and more effective to organize a "Million Atheist March". I have no desire to spend a whole weekend actually talking to some of the doofuses and fucktards in the atheist community (to be fair, I can't see those who think I'm a doofus and a fucktard wanting to spend a weekend talking to me either) but I could be persuaded to spend an afternoon hanging out in the general vicinity of the doofuses.
(The capitalist media would probably ignore such a march, but "A Million Atheists Kiss Ass at Unity Convention" doesn't smell like news, and it would be difficult to see how the purpose of unity would be served by the headline, "Controversy Breaks Out at Atheist 'Unity' Convention.")
If y'all want to go to a Unity Convention, knock yourself out: I'm not going to stop you. But I won't go. If it happens, I hope it'll be successful, in the same sense that I hope a guy falling from a building will be miraculously saved by a passing truck full of pillows. But likewise I don't expect it to end well.