I haven't done any reading about this but on the face it I don't think it's a great idea. Who else? Having worked for social services I can tell you the telling a group in a pub what I did invariably meant someone would have something to say about it. Not pleasant generally. I know police officers, teachers and others all face discriminatory stuff. Either all career based discrimination should be covered or none. I vote for none since I think it minimises the very real discrimination suffered by people on the grounds of race, sex, sexuality and the like.
I think this is little more than the current government's usual practice of pandering to what they perceive Daily Mail and Sun readers will like. There is a sort of kneejerk theme in those papers along the lines of saying that "Our Boys" are automatically living saints, which they themselves probably hate. It's quite dangerous, too. DS worked for a time in Wetherspoon's and said that easily the worst nights were the ones when a group of tanked up squaddies turned up, and they regularly had to throw them out because their behaviour was so obnoxious. If this law came into force, pub owners wouldn't be able to take that sort of action to protect their customers for fear of prosecution.