The meaning of this, as I interpret it, is that all gay people have straight parents, who did not teach them to be gay. That came naturally (or unnaturally, as some might say). IOW, being gay is not a choice or a product of the environment or learning. The implication is that straight parents should accept and love their children since the latter did not choose their sexual orientation but were brought into the world as they are by their parents.
There are a few errors and biases in the premise of the remark. First, while some straight people are offended by gay people, nowadays there is much more tolerance toward them. Second, the singling out of straight Christians is offensive since it targets Christians as a group as being particularly homophobic and paints nearly all Christians as bigots. Third, the majority of Christian religions, whether Catholic, Orthodox, or Protestant, are not taught to hate gay people for their same-sex attraction but disapprove only of their behavior based on the faith’s religious beliefs. And fourth, a minor point, it is not unheard of for gay people to have children, as well as straight people, of course. BTW, this does not mean their children have a greater likelihood of being gay.
I have nothing against gay people. As they say, some of my best friends…I also believe, based on research as well as gay people I know, that having SSA is not a choice. In addition, I’m in favor of gay rights, including gay marriage, and do not believe most gays have an agenda, as many others on this Forum do believe. But I’m equally opposed to stereotyping ANY group, including Christians, which usually means either Catholics or Evangelicals. Fighting biased attitudes with prejudice is never a good idea.