Accepting your anger without getting angry back, without "punishment," IS caring. That's what good parents do (or therapists in this case). Is it possible you expected what you "know" from childhood and this caring acceptance is foreign to you?

Kids act out to be heard when they are used to not being heard, and they don't always particularly care what the reaction is so long as they don't feel invisible. I see it in students on occasion who will get attention any way they can get it, even if it means negative attention. It's a learned behavior. Kids who are used to being heard by attentive adults tend to act out less often and with less vigor. They'll still do it, but when met with the same consistent acceptance and caring, with redirection rather than punishment, they will generally calm fairly quickly and be okay.

What your therapist is doing is modeling acceptance and caring of you, even at your "worst." But you may not recognize that's is what is going on.