You are coming across as defending this child-beater. Is that your intention? The child is probably kicking her legs in terror, not in happiness. Have you seen the video?
I'm sorry but this is sounding a lot like last Friday -- when 2-3 guys in 2-3 cars did/did not run a toll booth, did/did not say they were blowing up Miama, did/did not have an explosive trigger.
In the video on the Fox site the child is obscured from view during the hits so you can't for sure know if they were on the child or not; or if the bouncing of the legs was happy or convulsions. I think we need to see the kid before we burn the mother at the stake.