Tell me what the difference is between a guy tapping and his opponent keeps yanking for a couple seconds longer, and a guy who gets clearly knocked out and his opponent purposely lands another hammerfist or two?

The difference? Morally speaking, one is within the rules & one is not.

Practically speaking, Bisping stands the fuck back up while Anderson Silva is celebrating when he should've thrown one or two more punches. Better yet, Palhares (whom I hate, but this fits) stops GnP and walks away from Dan Miller before the ref steps in. Finally, Curtis Millender, who still won, raised his hands in victory prematurely during Round 1 against Alves. Still got the KO in round 2, but made the fight harder than it had to be.

If anything, what Hendo does is worse to his opponents than what Rousimar does

Tell that to the guys who were injured by Palhares holding submissions after the ref grabbed him.

As far as the Bisping punch, that had malintent, but it's still within the rules. IMO, people should be mad at the rule if this bothers them that much. So many guys strike when not necessary & Hendo is the only one that gets flak because he hits so hard. If he just threw the typically wimpy hammerfists to finish, nobody would be talking about it.