You don't overexaggerate something like bullying. You were bullied, or you were not. It is not something a therapist should doubt.

I was bullied as well at school and if my T would have responded like yours, I would have argued, and then, if not believed, I would have just leaved without making a scene. Nonsense going for having support on a senstivie topic like this only to have your words doubted. But luckily nothing like this ever happened to me in therapy.