CHristians are to reprove the works of darkness. I know it doesn’t comport with today’s “nicer-than-Jesus CHristianity,” but real Christianity is often confrontational. That’s not evil, especially when it’s done inconspicuously and without anyone noticing except the usher/greeter who questions me. I won’t be making a scene at all. And I’ll leave the premises promptly if they insist I wear a mask.
Does that bother you?
Yes, because you aren't going to worship, you are going for other reasons.
Don't like their theology? I probably wouldn't, either. But it isn't like there aren't plenty of options available.
And what significant thing are you reproving here? Is it your position that wearing a mask is incompatible with Christianity? Or is it possible that you are letting your other, more significant disagreements with your former church influence your action here? You may think it’s dumb to wear a mask, but is that really the issue? And will your confrontation actually do anything to encourage the people to follow a more biblical path or will it just serve to annoy people on Easter?