"Abnormal" has a very specific meaning. It is not used for everything that is just uncommon. It is used for behaviours that are non-normative. If you have an idiosyncratic way you use this word, ok, but communication is supposed to require and assume a common understanding of a language. So there is no point to discuss if abnormal refers to frequency of a behaviour in a population or in a normativity-related judgement of it, because in common usage it refers to the latter, because either we do not speak a common language or I have to assume disingenuity here (and leaning towards the latter in this case).

If the topic is about whether homosexuality is non-normative and heterosexuality is normative (with the actual, common meanings of the words), we can have a philosophical discussion on that.