Does that mean we should discriminate against Black soldiers? After all, they'd know what they'd be getting into when they signed up. Why can't they just soldier it out?
I don't get it, you're so worried about troop morale for homophobic soldiers, all while forcing gay soldiers to stay in the closet or face discharge which I bet does wonders for their morale and effectiveness.
Soldiers are expected to suck it up if that improves combat effectiveness. You'd have a point if the evidence showed that repealing DADT would seriously hamper troop effectiveness. The only problem is that almost all of the evidence says that repeal would have little effect on troop cohesion. All I've seen in support of DADT are some poorly done surveys, flimsy what-ifs, and complete disregard for history and foreign military policy. Even if we completely ignore the whole discrimination/civil rights angle, there still is not much if anything on DADT's side. Just look at history. I guarantee you that opposition to racial integration in the military was greater than it is with gays now. Yet they still went along with it. Were there a few hiccups, yes, but did it seriously hamper troop effectiveness, no. Our allies, the Canadians, the Brits, and the Israelis, all countries with very effective armed forces and soldiers, don't have anti-gay policies.
Some military personnel might not like it, but as you said, liking everything they do is not in the job description. Like you said, they know that they are signing on for a difficult job where their wishes won't always be respected, but one of the things that makes our military so effective is that personnel are expected to do things that they don't like, and far more often than not deal with it.