I've ridden all sizes and never felt bad about riding smaller bikes. In college I had a series of old Japanese bikes. One of the ones I had the longest was a KZ400. It was fun and would break the ton as they say in England but I had lots of people (who weren't riding by the way) say that they wouldn't ride anything smaller than a 750.
I think it's like big trucks. The bigger your truck or the more CCs you have the smaller your dick. Before you get too mad, I drive a Dodge Ram and have an 1100 GS.