I don't know what the answer is really. But I do wonder how much of this angst is down to the impact on individuals' (who go) enjoyment of the match, and how much is down to people worrying about the bad impression on TV, Rags taking the mickey, etc., etc.
I'll be honest; I don't go much these days for a variety of reasons to tedious to set out. When I do go, I invariably stay to the end. But the guy who goes at 80 minutes has the right to if he wants, just as a guy who buys a pint has the right to walk out of the pub with an inch still left in the glass. I don't know what you can do to persuade him to stay, although sorting out the transport issues would be a help.
As to atmosphere - more often than not, if you raise your voice or clap for more than two seconds some people stare at you as if they suspect you've just got out of a secure unit. The crowd is very middle class and conformist these days. Half of them are too busy talking about their clients or studying their phones to watch the match. I honestly don't know why a lot of them go, unless they think it's 'cool' or something.