Maybe they think nobody will want to have a traditional family any more, if they have the option to be gay, trans, childfree, etc.

Which makes me wonder if these conservatives are all closeted gay, trans, childfree, etc, don't want a traditional family either, and their “family values” are the only thing forcing them to have one.

I'm reminded of a story of a woman who, at a public discussion about this issue, made the argument that women must not be allowed to be lesbian. She reasoned that, if women were allowed to be lesbian, then all women would be lesbian, because surely no woman actually wants a man for a partner. After a few moments of awkward silence, and the agreement of no one (including a number of women in heterosexual relationships), she sat down without another word.

When "Christian values" mean "whatever American conservatives like," then I agree. However I do feel the need to remind everyone to remember to be fair about religions, as they can contain great intellectual value and represent a large diversity of thought that is far greater than the simple-mindedness being criticised here (to clarify, I'm not accusing you of anything, just adding to the discussion). Christianity has thousands of years of great minds who have written at-length about what the religion means and what values it stands for. From pre-Christian Jewish and Greco-Roman philosophical and religious influences, to the Church fathers, Mediaeval philosophers and mystics, all the way to Christian existentialists such as my personal favourite: Søren Kierkegaard. Really my point is that it is a vast intellectual tradition, and as relevant and necessary as it is to challenge the harmful dogma of American Christian fundamentalists (much of which, might I add, is rather unprecedented in the history of Christian thought, especially with regards to biblical exegesis), I do believe that there are an even greater number of Christians who are on your side and who follow a great many values and ideals from the religion that led them there.