When you say 'moral' do you mean moral as in within the discipline of Ethics? If we agree that the major premise of the non-aggression axiom is a truth statement: the initiation of force against an innocent person is immoral, then it's quite clear that homosexuality (being an internal subjective experience) does not and can not violate this. So, I'd say no, homosexuality can not be immoral as it doesn't violate the major premise. However, what if a child is taught to believe that homosexuality is "sinful" and deserving of self-punishment. Then, a child (innocent by default) may actually commit (even unknowingly) self-harm due to stress or out right violence against their own body (suicide as an example). Further, such a child may not have feelings of being homosexual until an adult - yet their brain has been 'taught' (physically altered at the synapse level) to believe homosexuality is sinful/wrong. I think a sound argument could be made that teaching a child who was born biologically, homosexual, and later as that subjective experience manifested itself - that this act by the parent (often as part of a mainstream religious group) is itself an immoral act. It can (and many times does) violate the major premise (see examples of homosexuals committing suicide - Alan Turing comes to mind).