Why is it childish to point out when someone is acting criminally — in a literal sense being a bad guy? Is it somehow more adult to act as though you are morally equivalent to an extortionist?
Calling someone "a criminal", meanwhile, degrades their status to that of a common mugger; someone in the lower class who needs to commit crime to survive, and who doesn't have the intelligence required to come up with a clever crime.
Hackers are generally aesthetes--we tend to value our intelligence, curiosity, etc. more than we value our moral fibre. We can appreciate stories like "A hacked into B to see if it was possible, and reported the vulnerability all responsible-like, but then they threw him in jail! How horrible!" because we think the positive-status from the display of intelligence makes it less likely, rather than more, that they were genuinely seeking to harm the people they hacked.
Because of this, I think we here are scared of being potentially associated with dumb, low-status, lower-class criminals more than we are of just being considered evil. People hire "evil, black-hat" hackers. Nobody hires a dumb hacker.
There is moral judgement involved with calling someone a criminal, and rightfully so. Taking what other people have created by force or extortion degrades society.