It wouldn't be so offensive if it weren't for the sudden spate of religious Christians imposing their views on others, today.

"Before Christ" or "Anno Domini" has been a convention in discussions of history accepted without consideration of their origin.

If it becomes a reference point historically, I see no cause to be offended. Christmas, for example, "Christ Mass" is a standard convention for a celebratory holiday without it having to be a reference for theology. It can be interpreted as a Pagan Holiday or a secular one which attempts to coerce the sun to come back and for people to light candles for this purpose, now exchanged for electric light bulbs.

I don't personally use this designation for a historical reference but as a convention, it stands, inho, without being inherently offensive.