If I see you on the street, I will at least give you a nod, a "s'up?", something. Even if I don't like you or I'm pissed at you, I, at the very least, will acknowledge you. It's common courtesy.
If you deny my presence or that you know me, I will, if I'm in a good mood, or angry, confront you.
If I happen to be in one of my more evil or predatory moods, I will delight in making you as uncomfortable as I possibly can by my mere prescence.
And trust me, I derive pleasure from doing that.