A buddy of mine got his beer spilled in a crowd like you are describing. Read on:
He told the guy "You owe me a beer" in a casual tone.
The guy replied "Go fuck yourself"
My buddy decided that it was necessary to defend the honour of this spilled beer, and asked the young man to step outside. My two buddies followed (I was not there, thankfully)
The guy met him outside with NINE of his friends, resulting in a 10-on-3 shitkicking.
Buddy 1: two black eyes. He was lucky and talented in the ass-kicking department.
Buddy 2: Jaw wired shut for 7 weeks. He said he did better than he looked, since he folded one guy's knee the wrong way and he had several teeth embedded in his elbow. He got an infection in that elbow though.
Buddy 3: (the one who needed to avenge his beer) was admitted to the hospital, and the doctor said "We are going to have to administer injection anti-inflammitories. If that doesn't bring the swelling down in about 8 hours, you are going to lose them, son..." He went for a CT scan, and luckily they were able to avoid an amputation.....
ON HIS TESTICLES.
All over a 2.50 beer. I laughed when I went to visit him in the hospital, and said "Next time, let me buy you a beer. From now on, just tell me 'Ben, someone spilled my beer. You owe me five bucks' and we'll call it even."