I've never had problems with Cubs fans personally. In fact, I married one.
The ones I know are very personable and knowledgeable about their team. Now I do know that a lot of Chicagoans send their kids to one Miami University, so that might also explain why the Cubs get such a good turn out at GABP. Compared to Browns fans and Phillies fans, Cubs fans are a pleasure to be around. And if you want to talk insufferable, wait till you hear a Yankees fan spend five minutes complaining about their bullpen or their guys not hitting or how, heaven forbid, they aren't in their rightful place at the top of the standings. I would put the Browns, Yankees and Braves at the top of my list for teams I hate because of their fans. I put the Braves in there because they win all the time and yet their fans are so spoiled, they can't even sell out their playoff games.