There's nothing I hate worse than the term "man up" being used in reference to fighting the law to get a reduction in an infraction.
Like c'mon, if a woman is getting assaulted and you're a guy who walks right by because you value your safety over saving someone, then I'm all for that person being told to "man up". Or in a hockey game when a guy does something cheap and gets challenged by another player than yes, that player should "man up".
There's many situations where the term "man up" is appropriate, but to call out someone's manlyhood because they want to exercise their right to challenge the legal system? Give me a break.
When I hear it/read it, in reference to fighting the legal system I see it more as bitter people who are mad that someone's using their precious tax dollars to use the legal system, so they want to throw out an insult to try and bring that person down and make them feel inferior.
It reminds me of that Russell Peters joke where he's explaining how the asian guy at the mall tells guys to "be a man" as a last resort when guys are walking away from his kiosk without buying something.