NOTE: After doing more extensive research, I've edited both my question and answer.
Imagine a situation where an evil person does an evil deed.
I don't want to get distracted with a strawman argument regarding the definition of "evil." Let's say the deed consists of murder, which most of us would agree is not a good thing. You could also replace "evil" with "immoral" or "bad."
A realistic example could be a world leader who decides to invade another country, then justifies it by claiming his country needs more living space or the other country did something bad (which it really didn't).
Now imagine if the media began promoting both the act and actor as good. As a result, ordinary citizens begin to believe that their leader and nationalistic war are both good.
What kind of fallacy is this?
As discussed in my answer below, the answer appears to be righteousness fallacy.