I am having the same problem now too. I've got 4 yorkies, 3 males and 1 female - all fixed, and a little mixed breed (don't have a clue what the little fella is - see avatar). Anyway, 1 of the males seems to have a snobbish attitude toward Radar, the mixed breed. Like your baby, poor thing just takes it, crying for help, and ends up bloody. We really can't pinpoint a reason for the attacks. Last night we were watching a movie, everybody quiet and calm, and out of nowhere, TJ attacks Radar. Its getting so bad I'm really considering rehoming Radar, just for his own safety.
I'm really trying with being alpha with them, but its really hard sometimes.