An adoptive parent is a parent. We don't specify "adoptive" all the time, and it'd be rude to refuse to refer to adoptive parents as parents because they aren't biologically related to their children in the same way.
We have done exactly this kind of language change in schools over that issue too, teachers often prefer "guardians" to "parents" in some contexts these days because some children won't live with parents, things like that. To pretend this hurts people is just counter to these examples we see in reality, it's just trying to use the words that apply to everyone, not just the most common case. The cost is so small, the attempts to push back on it seem actively spiteful, because there is no reason to contest it generally. The thing it brings to mind is the "but marriage means a man and a woman" argument from the attempts to stop marriage equality.