I was watching the movie Leon: The Professional. The protagonist, Leon, is a hitman — not somebody we traditionally sympathize with. The antagonist is a crooked DEA agent, pretty despicable himself.
Near the end, Leon is gunning down dozens of DEA agents who've been ordered by the antagonist to kill him. As the viewers, we're supposed to support Leon as he kills cops who have done nothing wrong themselves — they're just following (presumably reasonable, and since Leon is actually a hitman, perhaps actually reasonable) orders. Just because the person giving the order is the villain, they end up dead, merely doing their usually noble job (and honest cops generally have the viewers' sympathy).
I'm asking specifically about the DEA agents here: Is there a word or a phrase for this situation or literary device — where I'm made to feel that somebody is evil because of their association, where they've done nothing wrong, and they could even be considered the heroes from a different viewpoint? (Say, Leon were the villain and the cops had finally cornered him — I'd feel bad for these cops as they were gunned down). I checked the movie's entry on TVTropes.org and I don't see anything that seems to describe this situation accurately.