I don't see what Remco did that was so unbecoming. He didn't yell and curse at the guy, but just said "go away." The guy was on his wheel too long and clearly bothering him, which I can understand, because, on a climb, when one is training alone, one doesn't like someone sitting on one's wheel, period. Let alone the World Champion, who is following a rigorous schedule, and not just some Joe Shmoe out for a ride, but a highly visible public figure. Sure, the roads are public too, but you should know when to back off and not intrude. It's like Mario Cipollini once said to a rider who decided to tag along to his wheel too long during a training ride: "So, if you were at work, would you like someone uninvited coming into your office and watching you?"
I realize being a pro cyclist isn't like going to the office from 9-5, however, common sense should let amatuer cyclists know when to give pros their space while out training, unless otherwise told. And Remco allowed the guy to watch him for several minutes, before saying that's quite enough, leave me alone. I'd imagine the majority of pros would have reacted the same.