Yeah. But be genuinely nice. It should be due to loving feelings towards the individual.
Here is what Mother Theresa said. When asked how she could tend to the most disgusting forms of life lying in the sewers of India, she remarked, "I just picture Jesus in all his many distressing forms".
Hmmm.... if she can do it, we can. Look at the impression that woman made. We can at least practice one of her many good actions. Smile lovingly at everyone. It's easy to smile at friends. It is a test to smile at an enemy. Oftentimes, when the enemy realizes you mean him no harm, the countenance of the enemy changes as well.
I am not talking about insane examples like some maniac pointing a gun at you. I am talking about practicing everyday interactions on an individual basis. If all of us do this, maybe it would be harder to make people local terrorists.
Crazy people need medical care. I am talking about smiling when someone cuts you off. Try that one. Practice that one.