Some people simply don't cope well with complexity... the colours all need to be neatly inside the lines, the peoples of every country should always stay in their respective countries, and men should only get with women and vice versa... the world has never been that simple and never will be, and some people simply cannot cope with it.
Being in a relationship with someone is not entirely private... people notice that you live together, spend time together etc... I sometimes get the impression that some people are only comfortable with the LGBT community on the condition that they remain invisible and unnoticed... which is a ludicrous expectation.