No-one's perfect. But kids assume that of their parents.
I assume he usually does act kind and friendly, so this is "new' for him.
Just assume he's stressed out. When you start becoming an adult, you begin to realize your paren't aren't all-powerful and all-knowing, but that doesn't have to make them incompetents:P Believe me, I made that mistake, heh. Just give your parents room to be themselves. In all honesty, it's not your problem:P Unless they insult ya or harm ya out of personal feelings. Then they've crossed the line.
Good luck. Yer dad will cool off.