What would you do?
Rodney, that's a tough one.
My thoughts would be, just deal with him as little as possible, but be kind when you do as tough as it may be, in other words, be the bigger man! The last thing you want/need, is for him to be taking it out on your MIL, and it's sounds as if he may be the type.
It's sad that some people go through life with the attitude he has, they are truly missing out on so much.