I've had the same experience, where I felt T was "siding" with my family and it shut me down.

Telling T, after the fact, how I experienced it, helped him understand my thought process. It helped him avoid tripping that reaction with me, but it also helped me talk about it more. Now I can talk about it when it happens, in the moment, so I don't end up a hurt, spaced-out mess.

Sharing your reaction with your T is a way to bring it into the open so you both can work with it.