Utilitarianism does not support anything in particular in the abstract, since it always depends on the resulting utilities, which can be different in different circumstances. So it is especially unreasonable to argue for utilitarianism on the grounds that it supports various liberties such as gay rights. Rights normally express something like a deontological claim that other people should leave me alone, and such a thing can never be supported in the abstract by utilitarianism. In particular, it would not support gay rights if too many people are offended by them, which was likely true in the past.