The Enemy of My Enemy Is My... ?

Today I'll be reflecting on something a friend told me. In the first place, I told her it's bad enough labeling people as "enemies", but if we start going into the black-and-white area of whether some is "good" or "bad", then you will be obligated to tag someone who clashed with someone you don't like.

Otherwise, we do live in a world with grey areas. If a person confronted someone you consider "mean", you may approve of what they did now, until their brash attitude clashes with you in the future. Then would they become your "enemy" too?