"Ich esse Grammatikstraftäter als Abendessen!"
Though the whole sentence is - in terms of style - a bit limping. I'd rather use:
"Ich fresse Grammatikvergewaltiger zum Nachtisch!"
While it's not "dinner" but "dessert", it's a more common statement in the German language.
"Vergewaltiger" means literally rapist, "Straftäter" would be criminal - again, in terms of style it's limping since the word "Straftäter" is normally used in court only, "Verbrecher" would be more common, but sounds a bit dumb.
Last but not least - "essen" is usually more used like a dining human, while "fressen" is the more feral, animal-like style of eating.