Who decides that? In Christians circles especially, there's no reason whatsoever to get bent out of shape over something rather benign. In ordinary conversation, there's nothing wrong with referring to a fetus as a fetus.In ordinary conversation, there is no reason to use the term "fetus."
On that topic, I once had some friends over, and I gave them some lilly bulbs. The wife said "Oh, thank you for the lillies, I mean, bulbs", to which I replied "It's okay, I'm pro-life; they're lillies". We had a good laugh over it.