or Well any competitive human being in this planet would want to comeback, especially after a defeat like the one he took. A good father is supposed to support his son as long as whatever he wants to do is within a positive endeavor. The man feels bad for what happened to his son and I would feel the same way if he was my kid.
But in Khan's case... He's a big Pretender. He thought his speed would be enought to be an elite fighter.
Do you remember in those old cartoons when a character like Donald or the wily rabbit thinks of a great idea and then you see the dollar sign in their eyes? Well that's what khan's dad sees every time he lays his big old eyes on his son.