Anyone who sends merit to enough users will eventually sent some merit to some dodgy member who abuses/break forum rules.
If said dodgy member posts a good post, the Merit is deserved. Let the Mods deal with rule breakers, that's not what the Merit system is for.
I sometimes think of Meriting a plagiarising Newbie right before he gets banned, just to make it hurt more. But that would be Merit abuse so I don't do it.