I was at the World Championships in Belfast 2001 when Solis stopped him and Haye wasn't complaining...got hammered with right crosses because he kept dropping his left hand..hasn't learned much since..he was doing the same thing against Mormeck.
He definitely wasn't 'unconscious' at the conclusion. If they think that, they haven't seen the fight. He was on his feet when the referee (rightly) waved it off.
There is a BIG difference between just dropping your left hand/keeping it low and fighting out of half guard/shoulder roll.
Haye can be HURT and HURT big. The sort of hurt that can get a fight stopped. In the pros he'll be able to come back from being hurt like that, as long as the ref is good. So being stopped in the ams isn't major in the pros. For example Lewis stunned Bowe a couple of times and stopped him but it hardly meant Bowe was chinny. He similarly got stunned/hurt in the pros but because it was the pros he could continue i.e. against Holy and Golota. Haye has recently showed against Mormeck that being hurt isn't the end of the world. When Thompson stopped him he was exhausted and clueless.
Perhaps Haye has a china chin, perhaps it was making the cruiserweight limit that took away David's punch resistance? He's been stopped once and down heavily twice, in other fighters Personally I reckon it's a bit of both. I don't think Haye's chin is a complete dead loss (he'd have never won the undisputed title otherwise) but it's looking fairly clear that he's no Oliver McCall in that department either. His chin has just about held up to win the world title at cruiser, so that's one less ambition he needs to worry about. We'll have to see how he takes a heavyweight punch. I would imagine many great fighters have been KO'd in the amateurs.