In this scenario I see a possibility of the horsepeople being a little rude to begin with and the bikers blowing their initial rudeness out of proportion. This is what tends to happen when waring societies are invited to the same party...the Capulets and the Montegues, The Jets and the Sharks, the Hatfields and the McCoys. You have them both in the same place, something is GOING to happen and somebody is going to exaggerate it to his pals to escalate the whole war and to make themselves feel like they have the right to feel the way the do about the others...
Well said. Hits the nail on the head