None is so blind as he who shall not see....go check the tape and then come back and give us your take.
Short and simple. It was legal and no, it wasn't from behind. However, I wouldn't have any problem with banning it if all the cheap shots taken in the "piles" were eliminated and those are dished out frequently by those big DL's (Wilfork, NE ???). I say since this continues, as long as the opposing player is not otherwise engaged, take his legs out. Perfectly legal and fair.
Besides, it's not as if Tucker dove straight into Abe's knees for crying out loud. That would have been cheap, but it wasn't so get back to the tape and see for yourself....