Of course he made an effort to tackle Ben after he was tripped. You can't expect a player to just fall to the ground and stay there until the play is over. And the reason he hit Ben in the knee is because he was tripped and was falling. Had he not been tripped, it would have been a perfectly legal tackle (I'm assuming).
Again, what was he supposed to do ... fall to the ground and lie there until the ref blows the whistle?
Had he not been tripped and just dove at Ben's knees, we wouldn't even be having this discussion. But that isn't what happened. Gilbert got burned on the play and stuck out his leg to trip him. Had he not been tripped, it would have been a clean hit. So at the very least, Gilbert is just as responsible as Brock. Unless, of course, you expect him to just fall to the ground and remain there until the play is over.
I'll speculate ... had Gilbert not tripped him, it would have been a clean hit. To assume that he purposely aimed at Ben's knee, you'd have to conclude that he consciously made that decision in a split second after being tripped.
I agree that he purposely hit Ben. That's what he's supposed to do. The argument is whether or not he purposely targeted Ben's knee. And I say no. But whether it was intentional or not, if you hit a QB in the knees, it's going to draw a flag. And rightfully so. But if it isn't intentional, is it worthy of a fine? According to you and Goodell, I guess it is.
Just out of curiosity ... were you fine with all of Harrison's fines last season?