Well, yes. But an employer can also just say they don't want to hire someone who may have committed sexual assault, domestic violence or even drunk driving, regardless of what a court or jury decides. And in MLB and NFL's case they explicitly can render their own punishment separate from the legal system just because someone's been accused (as with Urias and Herrera).
DeShaun Watson has also never been charged with a crime, but I don't know many people who don't think he committed some, and the NFL has actually made its policy even stricter since his suspension.
The NHL has not said these guys can't play, nor did it suspend them. They all took a leave of absence, and their teams all chose not to offer them contracts after last year. Now, I'm sure the players all realized there was nothing in it for them to try to play - either with the league or the court of public opinion. And Hart is not allowed in the US because he's Canadian and has been charged with a crime there.
Another quirk - this incident would not violate any conduct clause in their NHL contract because none of them were signed to NHL contracts at the time it occurred.