I wouldn't question the PIC's call to return, but I sure as hell would press charges if I did make that call. IMHO, one should back up their decisions with actions, and if there was a charge that the crew could have filled (even if UA didn't file them as a company) I would have. I am 98% sure there was at least a single charge out there that could have been pressed by the crew, even if it was obscure and had little penalty.
I have filled charges against a passenger when UA chose not to. They backed me up (covering their bases, asking if I needed counciling...) to a point (mostly likely becuase it happened right in front of a city of Chicago surveilence camera,) but I turned over the police report to them for their records, and when I went to get it back, they stalled in getting it to me, and then "lost it." By then I didn't want to go thru the trouble of taking a day off to go downtown to get a copy of it, only to then appear again in court on another day on "my time", and I regret this decision of mine. Stand behind your actions as a person and make the sysytem work by pressing charges! Even if the penalty is not severe, it gets it on record and if there ever is a next time, then it may be used then.