Speaking from personal experience, I find it most likely that at his core, your dad is just trying to help - especially if you are outwardly showing frustration about your acne. But if you feel insulted, that must be coming from somewhere.
I was often told I was overreacting or “too sensitive” about everything, especially regarding my skin or my body. “Get over it”, “You’ll grow out of it”…there was no shortage of dismissive phrases thrown at me over the years.
If your father has ever been insulting or dismissive of your feelings towards your acne, that might be where that feeling is coming from. I really don’t know, I hope I’ve helped? >_< Perhaps have a chat with him about it, see what transpires.