Since I've started cycling, I've joined many pacelines and drafted behind countless solo riders. I'm always careful to make my presence known and if I'm unsure, I'll follow from 2-3ft to be safe. I gladly take my turn at the front when my time comes or when asked to do so. I've met a lot of people this way. I catch up to them, draft for a while, and then pass them to take my turn at cutting the air. As we pass, we exchange greetings, introduce each other, etc. All very friendly. Today however, I've had my first bad experience and I'm a bit puzzled. I was riding along and this 50-something chubby guy passes me on his shiny new Colnago with Dura Ace and pro-team jersey. Since he passed me slowly, I joined in his wheel. Seconds later we start climbing this 1.5km 4% hill. The guy stood up the whole time and was spinning with the chain on his big ring. "Pretty good for a guy his age", I thought. Once at the top, he looks back, obviously seeing me. He rides for 5 more seconds then slams on the brakes, locking booth wheels. I almost rear-ended him but luckily was fast enough to avoid him. As I swing around him, he yelled "get off my wheel you fucking wheelsucker". Holy cow! He was smoking hot so I just keep riding. A few minutes later I slowed down to let him catch up to me and explain that a little hand gesture would have been safer and more appropriate. His reply is "next time you wheelsuck me without an invitation I'm gonna f_ing hurt you". Wow. I then noticed a big tattoo on his arm. I didn't insist and rode away. Is there a cycling etiquette rule I should be made aware of? What's this guy's problem and why was he so upset?