Someone has probably just discovered your work and found it systematically wanting. By "many users" I mean that many of the more recent comments are at minus 2-3 and there are only a few upvotes, so other people don't generally disagree.

You essentially accused the community of being ashamed of being atheist when you said:

Though people have been reluctant to admit it because I personally think it's unhealthy and reflects poorly on the site.

We aren't ashamed. As Jack said to you in a parallel comment, we generally think the question is a solved problem. We aren't interested in having the same basic conversation over and over again.

Accusing us of being ashamed of the position because we don't throw our atheism in your face makes it hard to interpret the rest of your comments as saying anything beyond repeating the basic apologetics. And we've heard the basic apologetics a million times.

Once the lurkers think you aren't interesting, they'll downvote - and there are WAY more lurkers than commenters. Given that, your karma loss isn't all that surprising.

Possible, but given that all your comments are on only a small number of threads and arguing for the same basic points, it is also plausible that someone just went through those threads an downvoted most of your comments while upvoting others. I for example got about +20 karma from what as far as I can tell is primarily upvotes on my replies to you.