I've pretty much lost all respect towards Punk since leaving WWE. It's not because he's left the WWE, you should leave if you're miserable, but it's just all the things that've come out about him in the years he left.
Regarding leaving WWE, if there was anyone who had less of a right to complain about how he was being used/treated, it's Punk. He was making millions of dollars, was the longest reigning singles champion of any kind that WWE had for a generation and was consistently used, booked and touted as one of the top stars in the company. However, that wasn't enough as he allegedly wanted the "John Cena push" despite the fact that he was always confrontational and antagonistic backstage to almost everyone, never showed any real loyalty to the WWE brand and not having John Cena's work ethic. What respect I did have for his position lie in his protests against the part timers coming in, showing up a small handful of times a year, using their name & recognition to get paid a small fortune for it and take prime spots on the biggest shows of the year and ultimately taking spots from guys who worked round the clock all year, etc.. Punk obliterated that respect by signing with the UFC despite a complete lack of MMA experience. Punk doesn't mind taking someone else's spot, someone who works his ass off training for years or to use his name and past WWE accomplishments to sign up for six figure fights in the UFC; it's even worse in Punk's case as he's shown the two times he's fought that he's like a fish out of water and there are legitimately talented fighters who can't get the UFC to give them the time of day. Punk doesn't mind bigfooting as long as he's the one doing it.
As far as the lawsuit with Dr. Amann, Amann should've simply stuck to suing for slander instead of for lost wages because it didn't really make sense. Punk's claims could have legitimately caused damage to his professional reputation but the lost wages thing didn't hold up considering he was still working for WWE. It probably hurt Amann in the eyes of the jury, so yeah, he should've just sued based on the potential damage to his reputation.
Regarding his situation with Colt Cabana, I didn't know that Punk was so vindictive that he'd pretty much sever ties with Cabana just for him visiting with friends who happen to work for WWE. To be honest, that sounds more like something I'd expect from some of the higher ups in WWE rather than Punk. I've read that Dave Meltzer is stirring up the conspiracy theorists by stating that the falling out beween them is something WWE had hoped would happen all along, only that it happened too late to help Amann in his lawsuit.
WWE is the big ol' corporate entity, which means the company is often cast in the light/role of being villainous as corporations often do utilize tactics that seem to regular, workaday dicks like the rest of us as being underhanded, which is probably true in some cases. Punk just continues to tarnish himself and now he pretty much has only the hardest of hardcore fans still standing with him. His professional reputation is in the trash, his MMA career is one of the biggest jokes in all of pro sports and he's tossed his best friend & consistently biggest supporter to the wolves knowing good and damn well that Cabana probably can't pay those legal fees.