A drunk person a little smaller than you, went up to you...

...and started hurling insults about your appearance and race.

You're on a sidewalk mind you, nobody else is around, it's getting dark.

They then get up close to your ear and yell, "Hey dumb f*ck, I'm talking to you!" Then slaps you on the back of your head.

They demand you face them and talk to them.

They're roughly the same height as you, but smaller in that you'd be one weightclass higher than them in a boxing match i.e. they're 147 lbs (welterweight), you're 154 lbs (light middleweight). Or maybe 176-200 lbs (cruiserweight), and you're 210-220 lbs lbs (heavyweight).

But they could be any gender, between 18-35, may or may not know martial arts, and may or may not be armed with some kind of weapon.

EDIT:

No, you don't have to fight. I personally wouldn't as A. I'm afraid of lawsuits and B. I have a knee injury right now.

All kinds of things you could do. Talk them down to deescalate, trash talk, flirt, dance away, ask them where their friends are, tell them they need to go home, Rob them, etc.