Hmmmm...no. He was fired because he did something wrong. There are many things a person can be fired for that do not require criminal charges. I suspect that sending unwanted nude photos or junk photos could be criminally prosecuted.
You know if his actions caused sponsors to say "we are taking our money elsewhere" then darn right he should be fired! He is costing the owners money.
Also, if a lawsuit arises, the Mets could be named. Firing him gives a judge a reason to toss them from the case. So yeah, that is a good reason to fire the idiot.
In a job like that, there are no "after hours". He is not some mill worker who clocks out at 5 every day.