I did a cross country tour in 2000 that happened to pass through Sturgis during the motorcycle rally. Hundreds and hundreds of Harleys passing by all day long! Made my ears ring. They seemed generally friendly, I think they were having a good time and could see that we were too in slightly different ways. They'd cheer us on climbs and on fast descents, we got more than a few waves and thumbs up from them as they passed. I've had a couple of less pleasant experiences with motorcyclists too, but that particular period of time seemed to demonstrate that the was some common ground.