I'm with ya OP, I could easily hit my knee on the stem if my knees were pointing inwards a bit and the bike was swaying in a hard sprint up hill. Heck I can almost touch my knees to the bar (and I have a 110mm stem on one bike, and 120mm on the other), and if the road was steep enough I could see even that happening.

I'm betting almost everybody who thinks you're crazy could go get on their bike right now, stand and lean over the bars (pretend you're cavendish) and easily see how a stem/knee collision could happen.

As for the fix, I dunno. Try working on sprinting technique is all I got.