I think there are good, educated, arguments to be made against having gays openly serve, the best of which is probably that having a sound military is far more important than nearly everything, making the military a bad venue for advancing social policy.
When society at large has reached a point (and my opinion is that we are headed there and, like it or not, that point is not too far off), where homosexuality is by and large accepted by mainstream society, then it will make sense to let gays openly serve. Most of the ridiculous stereotypes that make this an issue (many of which conveniently appear in this thread) will by then have dissipated so that will be far less of an issue than it would be today.
But until that happens, whether it should be so or not, moving past DADT presents a real danger to good order and discipline (again, one need look no further than this thread confirm that is the case) and using the military to further a social cause, no matter how just that cause may be, it too dangerous. Social experimentation needs to happen organically and in places where the disruption won't threaten national and global security. Once that's taken place, then the results can trickle in to the military where, thanks to the social evolution that took place outside our bases and posts, it will be much better received than it would be if we tried to create that social change within the military.