God advice for both inside and out really.
That said, I do have to say, when you "everyone behind bars is a criminal and a bad person, right?" it got me thinking. I know you were speaking about the judgment of the general public. One thing I learned as a lawyer and it was a lesson I really needed, is not to judge. Some of the most honest, forthright, decent people I've met have actually been over the interview table in jail/prison. Did they make mistakes, yeah. Did they get themselves in trouble? Yeah. But, many of them were decent, honest people deep down. I've also met a lot of assholes, but hey, I've met them out on the street too.
There was a guy, he was a mechanic and a former bad drug addict, he killed his wife in a coke-fueled rage. He was no humanitarian and he was wrong and desereved to be exactly where he was. However, he became my client because certain people tried to take the body shop he owned and his home from him. These people were essentially trying to rip him off and prevent his minor chid from getting any of it. I'm proud to say that one of my last acts as a laywer was to shut that shit down. Sober, the guy was really, not horrible. He's spending his life inside and his property was a sepaerate matter. He's dead now, but at least his daughter inherited the home and whatever money was left from the body shop.
You always need to be careful about who you deal with, but you also need to have an open enough mind to not judge.