I've been in a similar situation. In this day and age, one never knows how far things can go. I said I was sorry when he screamed at me. The second time the nut-job approached me I told him, "I understand your point, I'm very sorry. You are making me feel uncomfortable. Please leave me alone, now." I then stopped my bike on the side of the MUP and watched him ride away as I pulled out my cell phone. If I didn't have cell phone coverage I was prepared to go to plan B....