And how you can safely interact with them!
The thing not to do is hate these people. They have good reasons for being the way they are.
Also, the thing not to do is pity them. They don't need pity. They are perfectly in control of their behavior. It's not up to you to show them any sort of light. They know it's there. If they want it they'll get it.
What you can do:
1. Be yourself. Don't hide your smiles. Don't smile when you're not happy just to annoy them. If an asshole asks you what you're so happy about, just say, "I just am." Joy, like any emotion, does not need justification.
2. Consider the cause. An asshole is in short someone who is disappointed. In order to be disappointed you have to have standards and have had hope at one point. Therefore assholes are actually quite sensitive insightful people who have simply observed some harsh things and have accepted these harsh things as an almost constant influx. He has realized that life is disruptive and painful, realized that he probably won't get what he wants, and for sanity's purposes has therefore resigned to accepting the negative but commenting fiercely on it as his only way of still having an identity. His criticisms of others are objectively correct. He's honest. He's both respected and disliked for that because we all know white lies keep the love. Not saying things that are truthful but painful keeps the love. An asshole is someone who sacrifices guises for reality. Respecting the honesty of the asshole will help you to not take the asshole's disappointment behind the honesty as personally. Remember--in order to be disappointed you have to have standards. Standards are good.
3. As they are cutting everything down, assholes are looking for rays of light. Do your best. Be integral, but don't blow your own whistle, and the asshole will most likely leave you alone.