I think that it stands out more in people's minds when a character like Willow slut-shames and calls Cordelia a "skanky ho" in Phases, or calls Faith a "slutbomb", because the episode calls attention to it being OOC and we are just as surprised as Buffy and Tara were at Willow saying that. It stands out in people's memories more than a character casually making comments about other women that just slip off the tongue, that's somehow seen as more excusable/not such a big deal, cause again that's just how that character is?

But yeah, I don't remember any of the scoobies slut-shaming Faith particularly in season 3, if anything they were pretty impressed by Faith's brashness in the beginning and thought that she was really cool when she would do stuff like hit on Giles, or tell stories about sleeping naked. Willow originally took issue with Faith because she was jealous at Buffy starting to hang out with her more, and she saw Faith as being so much cooler and more exciting than herself. I don't think that was ever any subtext of "Why does she want to hang out with her" though, it was more hurt at not being included