"Hurr durr destroy religions" is neither the point nor a goal, fruitperson. It's to stop using excluding language when possible, particularly for general use stuff. Things like this topic is small potatoes... but it is potatoes. And every little bit helps break a cultural belief that it's okay to just casually disregard huge swathes of the human population without good reason. Even just suborning a previously established system with more currently palatable terminology is pretty good -- what christians did to winter solstice is a pretty good example case of how to do this sort of thing, in general.
People get influenced by subconscious junk all the ruddy time, and stuff like the AD/BC thing is precisely the sort of venue that sort of thing works through. Few singular instances are major influences, but the issue is in congregate -- thousands of little things working together to foster, say, xenophobia or bigotry or whatever particular strain of virulent ignorance is in vogue at this moment. With this one, it's one tiny message saying, "We don't give a fuck about anyone not part or descendant of the christian cultural hegemony" and another tiny one saying, "Christian terminology in our culture is normal and acceptable, even if it's effectively snubbing parts of our population". Sure, it's just tiny ones, and singular instances, but in the face of dozens or hundreds of similar messages, it adds the zog up.
Is it really not evident why things like that shouldn't be changed, when possible?