What is the justification for social conservatism for an Athiest?

I've encountered many atheists from Russia or Eastern European countries who hold socially conservative views. I can think of Carl Benjamin (Sargon of Akkad) as well, who's right-wing but also an atheist.

Since so many of the conservative viewpoints, like not accepting gay people, come from religion, I can't understand what the justification behind these viewpoints are if they're not rooted in religion.