I definitely pay attention to how someone treats others, and if their behavior is not nice, I tend to avoid interacting with them as much as possible.

Unfortunately, sometimes at work, we still have to interact with people who treat others shabbily.

In that case I do my best to make myself a smaller target and/or stay out of their line of fire as much as possible.

In situations that I cannot do that, I get whatever interaction is necessary over with as quickly as possible so I don't have to remain around their negativity far too long.

In more extreme situations (bullying/abuse/discrimination), I won't hesitate to go to HR/EOO/ADA about it, though.

To sum it up with what was once a popular bumper sticker ...

MEAN PEOPLE SUCK!