I have made the same observation. Serious bodybuilders tend to have larger cocks. I haven't come across any with smaller than average sized cocks. The perception is really about perception. Their cocks are perceived to be small because the rest of them is so large. The posing trunks that smash their meat don't help, either.Honestly I haven't come across a bodybuilder that was average, all were on the large side, and I've met quite a few "serious" bodybuilders. If anything, it's just a proportion bias, anything will look small when your legs are the size of tree trunks (and jealousy obviously).