I think being stuck in the past is definitely part of it, but in my opinion the main reason they don't seem to talk about it at all (unlike race which they mention at every single opportunity) is that it doesn't fit neatly into the Culture War. I will explain.
I'm not as down on SA as the rest of you. I still post there from time to time so I'd be a hypocrite if I were, even today it still has a lot of content that I find funny and/or interesting, including from 'hysterical troons'. However, one thing that is absolutely true is that it has become completely politicized over time. That process started at least a decade ago, and at this point it just permeates everything despite occasional pushback from straggler goons such as myself - and I would say there are still quite a few of us.
Most goons are atheists and it makes logical sense to assume that fundamentalist Christians would be their natural enemy for various other reasons as well, but it's not that simple. They tend to be extremely online, and it's inescapable that many of the bad people on the Internet, Redditors, the alt-right, the Dork Enlightenment, etc. are usually rationalists and atheists who make fun of Christianity. Worse still, they occasionally even dare to criticize non-Western religions.
How do they deal with this? First, the important thing to understand is that every goon is implicitly expected to be a loyal soldier in the binary Culture War. All of your opinions are expected to align perfectly, both with themselves according to a preconceived pattern based exclusively on the current state of American politics, and with those of other goons, and you will be scrutinized constantly to see if that's the case. There is some ideological wriggle room as long as you're not too explicit about dissenting, but not much. So when it comes to something like religion, where there is not a simple black-and-white position to take that cannot be construed as being problematic in some way, rather than being individuals with their own personal, nuanced set of opinions who accept that the social world is complex, they choose to ignore the subject entirely.
