The only thing that bothers me is that all the articles I've read on the debate, talk about it as a debate among the Democratic candidates. A media forum should at least make an attempt at seeming non-partisan.
At this point in the process, the debates are for the candidates of one party to debate against the other members of their party for the party's nomination. So I don't think it would be appropriate to have candidates at both parties in the same debate at this time. (Though just because it isn't normally done, doesn't mean it couldn't be done).
But LOGO should really offer to host a Republican candidate debate on the same issues, in the same manner etc. Now it is highly likely that no Republican candidates will accept the invite, but the offer should still be extended (the refusal to participate will speak volumes).
Also some of the more pro-gay candidates may choose to participate and that will be a good thing, showing that not all Republicans are gay-baiting twits. There may also be the possibility that some of the fiercely anti-gay candidates may elect to participate so that they can make it clear that they have never meet a queer they didn't hate. At least it would clarify their position and let folks know where they truly stand on these issues.