With people like that its best to not engage at all.
Ive only got into a couple of physical fights and im not a fan personally...
The most memorable one was some short middle aged bloke harassing a female bartender friend, i tapped him on the shoulder and told him to clear off and he did, but came up to me when i went outside and shoved me, I said something like "leave it out mate." but he called me a see-you-next-tuesday and shoved me again and spilled most of my beer, so I dropped the (fortunately plastic) cup containing the dregs of my beer and lamped him one. He came in for more but three or four randoms got in his way, and then he cleared off. It felt good, but at the same time made me worry i was going to bump into him when he was with some friends. Also punching someone in the jaw bloody hurts!!
If i hadnt already had a couple I would almost certainly not have done that, and just informed the security at the door instead.
Fortunately it was a couple of years til i saw him again, and he recognised me in a different bar, he came up to me and i thought "oh here we go..." but he apologised and offered to buy me a drink, which i declined because i was driving. Said "thanks though" and that was the end of it.
If confronted im usually just polite and might give an incincere "sorry mate" which usually does the trick and results in them murmuring something to you and wandering off feeling like theyve won.
Better than escalating and squaring up to them, only for them to pull a knife on you!
Its usually the weedy little shrimps that provoke random people like he did. Small man syndrome.