I think what will happen at clubs like United, Liverpool and Arsenal is that the fans will realise that peaceful protest is a complete waste of time because the owners simply don't care, and the hardcore fans will start to do more to protest. Fans won't just stay sat in their seat with a green and gold scarf on, they'll run onto the pitch and handcuff themselves to the goalposts. They'll invade the pitch during games and cause the Premier League to deduct points, or make United lose the match 0-3, and eventually, United fans will be banned from the stadium, forcing a 100% boycott.
Nobody wants to see that happen. I'd hate it, but it feels inevitable. I'm not a staunch United fan, but I can understand the anger from United fans and I feel like an escalation of the situation is inevitable at this point. The fans won't just protest with a green and gold scarf, there'll be some who are willing to risk a lifetime ban to hurt the club where it counts. I'm not sure what the FA rules are, but if fans actions starts to mean that United lose games 0-3, that's what the Glazer's will recognise. If that happened 3 times in a row, they'd be thinking more about selling at that point than they would from a decade of green and gold protests.
What happened at Charlton feels like a glimpse of what we will see in the Premier League at grounds like the Emirates, Anfield and Old Trafford. These owners will only leave when they're punished with fines, losing games, empty stadiums, point deductions etc. and fans can make that happen. It's an ugly situation but it's those scummy owners who've started it, not loyal fans of good, honest clubs with proud histories.