Some motorcycle forum guys who I rode with to a poker run (dumb mistake, Harley people hate us crotch rocket types, but nothing happened at the picnic) did wheelies on highway 80, at full speed, and scared me to death. They did it really close to my motorcycle too. We were all in the left lane and I was uncomfortable with how close they were riding to one another, and to me..... never rode with them again and on the way back they actually lost this one motorcyclist we were supposed to show to the freeway because they got impatient.
In 34 years of riding, I've gone on precisely one group ride, and had pretty much the same experience you had. (We rode from Milwaukee to the Sheboygan Brat Fest, in a group of maybe 100 bikes, predominantly Harleys. We were on our then-new Honda Goldwing.)
The Harley attitude seems to be a scorched-earth approach to riding, with wildly unnecessary risks (riding too fast, too closely, next to people who don't know how to ride, swerving in and out of traffic) combined with an alcohol-fueled, asinine, "let's **** off as many motorists as possible" attitude. (Example: Blocking the left lane of a 4-lane divided highway, so no cars could pass, etc.)
Combine this with their penchant for making their machines as annoyingly loud as possible (despite having pathetically little power), IMHO means that Harley riders have become to riding what Walmart shoppers are to shopping.
Also IMHO, and quite conversely, there are plenty of intelligent, competent, and safe Harley riders. Harleys are beautiful machines in their own right, and -- in the right hands -- they are wonderful motorcycles. Unfortunately, there are a disproportionate number of bad riders in their ranks, as described above, who tarnish the Harley reputation with other riders (like me), as well as with all of our reputations with motorists who don't ride and can't tell the difference between a Harley and a Kymco.