Attacking something over its Christian roots that is no longer generally understood to be Christian is, in fact, anti-Christian bigotry. There is no policy of attacking things with any religious roots, just ours.
It say AD "was conceived around the year 525 by the Christian monk Dionysius Exiguus. He did this to replace the then dominant Era of Martyrs system, because he did not wish to continue the memory of a tyrant who persecuted Christians." So AD itself was a neologism to avoid mentioning something offensive (or someone offensive, Diocletian).
It's probably related to the pushiness of the religion. Like, something similar might happen with Islam, or Hinduism these days. But probably not Zoroastrianism or animism. On the other hand I think it's silly and resembles damnatio memoriae.
You’re not separating what you call “pushiness” from mere presence. Notice how you picked two minuscule religions with tiny numbers of believers, and therefore very little community, worldwide?
This is about mindshare, or brand awareness. I removed the branding from a garment. Does that mean I took a dislike to the brand? Yes, because I thought about the vibes it gave off (it brought to mind sticky, crunchy dancefloors) and decided I didn't want to promote it. But this was the brand's fault for trying to use me as walking billboard in the first place, which forced me to pick a side on a matter I wouldn't otherwise have thought about. If I'd decided I liked it, I would have worn it proudly! If you're lucky enough to have mere presence, which means you're embedded in the culture in names and phrases and clothes and statues, some people are going to opt to convert that into your mere absence, and the correct response is not we are being picked on but fair enough, can't win them all.
I say correct, this of course depends on how embattled you are, how unfair it all is, and on the general moral situation.