you know what's funny? It's so easy to say this now but I think all of us who were rooting for Cain (whether the rest of you will admit it or not) had our stomachs drop at the beginning of round 1 when Joe was like "CAIN'S HURT!!!"
and the replays after the round actually did show some good punches connected. So the thing is, if JDS had just been able to follow up a little better, or if the punches had landed a little better, the JDS fans would be saying exactly what you (OP) are saying except the opposite. They'd be saying "Can we all admit now that the 2nd fight was a fluke?"
It's pretty clear that JDS is capable of beating Cain. The fact that he kept his power the entire time and kept landing that left elbow certainly had me nervous.
I definitely don't have to see him beat Cain a 2nd time to know that he can do it.