There's an important difference between airing one's beliefs or preferences and merely possessing them. Many feel that criticizing people for beliefs is unfair, since beliefs aren't voluntary and one can be held responsible only for what's voluntary. But some philosophers doubt this (see e.g. Robert M. Adams's wonderful paper 'Involuntary Sins'). Imagine someone whose beliefs about homosexuality are unusually vicious -- perhaps they think gays should be tortured. Even if we think this person's beliefs are involuntary, we'll probably be tempted to criticize them. (It may be, of course, that this kind of criticism is of a different kind from that we use in the case of voluntary action.)

But this general didn't just hold these beliefs. He uttered them, and that is something that he could be held responsible for in the ordinary sense. Here I suspect people might want to criticize him from two angles. First, it might be thought that he was violating some principle of professional ethics. He was speaking as a member of the US army, and shouldn't have said anything that was against US army policy or might plausibly be seen as bringing the army into disrepute. Second, his comment raises questions about the limits of freedom of speech, most famously discussed in J.S. Mill's *On Liberty*. What one thinks about such limits is going to depend on one's general moral view. But something like Mill's view is quite common: that speech can be criticized if it is potentially harmful to others. Given that people often attack or discriminate against gays, speech that encourages such action should be criticized.