No, it's what the term "assumed risk" is for. If he was really that bad of a biter I wouldn't give him access to the aisle. Anyone on a horse property is assuming a presumed risk, and the death that happened was an assumed risk of jumping.
He didn't 'kill' someone. He refused a jump and tumbled over it because he couldn't get himself stopped in time. That's an accident. He didn't seek the guy out and stomp him to death.
I'm surprised at you both. 
That's ok. I'm kind of surprised at your response too. People have different opinions, depending on where they are coming from I guess.
If he was just a stall biter, that's one thing. But if only 2 people could ride him, that points to a more serious temperamental problem. It doesn't sound like a normal "fall over the fence" accident, but without knowing more facts we can't say for sure.
But if, after that accident, he had dumped another rider and then jumped on top of him, there would be a liability problem. Unless the rider knew of his temperamental problems and his tendency to jump on people . . . then there might be an assumption of the risk. But it would be a jury issue for sure, and trials are expensive . . .