You're better off with people like that being out of your life anyway. The old...one bad apple phucking up the whole barrel thing applies. haha
The Woman used to work in an environment where a certain person would roll into work and the entire workforce in her area would go from jovial to misery like flipping a switch.
Poor souls like that are likely never to be happy and there's nothing you can do to change them. It's a drain on your mental batteries to try. They love spreading misery and bringing others down to their own miserable level. At the root of all that misery is a self loathing and self hatred and that's something only they can change. Most will not try.