"As long as she is happy.", is a really poor excuse for not wanting to take care of ugly stuff. "As long as we are happy" is what he should strive for, as his own happiness is more important than that one who resorts to violance.
It's rough to live with a partner, who's not looking out at least a bit for his/her own wishes. Doesn't look like he really wants to be happy. I'm really losing faith in MC here. Maybe Christina would really be more happy later in her live with another guy.