The issue is when you start saying things like that, dropping accusations like that, it’s not only about the person you’re insulting and you. There are other people in the equation. To my mind there are two elements to this:

First: say someone comes from a religious background and isn’t quite so sexually liberated as you and so already struggles with that internalized guilt. Call someone a slut in front of that person and all of a sudden they are witnessing something they’re afraid of in themselves being turned against someone as a weapon to hurt, and now they have to deal with more fear of the shame, this time from you. That’s the thing: you say you’d never shame someone, but how are they supposed to feel safe around you if they see you do it to someone else?

Second: the things we say and do inform the norms of social interaction. Every time you direct an attack rooted in bigotry at someone you establish, just a little bit, the norm that it is acceptable to do so. It leaves the door open for those who might not be so discerning as you to enter the conversation, participate in that bigotry, and then take that a step too far.

Like, sure, you can argue that the insult is coming from a place of “I don’t believe this is wrong, but I know you do, so fuck you.” But the way we handle these conversations dictates more than just that conversation: it impacts social norms as a whole in a way that spits in the face of common decency. I don’t think that’s something we should consider an acceptable cost.

Ultimately, I just think it’s unnecessarily cruel, and utterly pointless when we’re talking about someone who has so much that is perfectly valid to criticize her for.