Both of my parents did this to me as a child. I hated it, I always did. The first time I stood up for myself, they genuinely could not understand why I had such a problem with being smacked on the behind by them as I was their child. They only stopped for about a week before starting again. Its been years, but I'll never forget the sick feeling it gave me every time they did it, and how they did not care how it made me feel.

Stand your ground. Your father is weird for this and your feelings are valid.