My last T didn't use IFS but was trained and experienced in dealing with dissociated parts. I did not feel that she really accepted them, however, at least not their (unsocialized) motivations, if that makes any sense.

Hence I felt like they were not welcomed or wanted there (just like in the rest of the world), in anything other than an intellectual or clinical sense.

Pushing back and locking them up wasn't really an option anymore -- probably because I didn't want to. And I was grown and if that's what was needed in order for me to survive still, then I wasn't sure I wanted that.

What worked for me was to find intellectual justification for the existence of those parts and their motivations. And then there was a conflict with my last T in which I (adult) eventually, at home, "stood up" for one of the parts who had acted out and whom the T had shamed and put down. That eventually led to me leaving that T but -- fortunately I had some other social support by that time. And eventually I may be getting some internal support as well.