One day I ran into Lou, a wiry and intense Jamaican-American computer engineer and got into a stimulating conversation with him. The topic under discussion was one we more or less agreed on, but on subsequent meetings I came to realize there were many areas where we did not quite overlap. After a while, our meetings at the coffee shop became battles, every time I saw him come in, I cringed, and he always came with a laundry list of items (he obviously prepared himself for these meetings ahead of time) he was going to challenge me on.

Some of our debates became quite spirited. And he always seemed to steer the conversation away from those topics where we had something in common into areas where we disagreed. I really didn't feel like arguing with him, particularly in a public place, but he had an annoying way of throwing a factoid in your face that simply demanded a riposte. You just couldn't walk away from it, he would not leave you alone. And he would not give it a rest.

I started to notice that my former friends stopped dropping by my table to chat, and even perfect strangers in adjoining tables would move away to other seats across the room when he sat down next to me.
And when I left the place, instead of relaxed and and looking forward to the 8 mile pedal home, my stomach was in knots and I was pissed off.