This type of rudness is probably carried over from their everyday style of living. Their daily routine survives on crowding you out of the last parking spot, not waiting their turn to pass on the highway, and screaming foul when another kid beats their kid at a sporting event. We often use the term, trout park mentality, but that's only an expression and not the true root of the problem. Being respectful and courteous should be second nature. You have to feel sorry for people with that attitude, and even sorrier for their kids having to watch their parents act like idiots. There is no good way to handle a situation like you experienced and we all see so often these days. For me, it is best to move on and go back to enjoying my day on the water. The people that crowded you out, will do the same thing to someone else tomorrow, no matter what you say to them.