However many walk out you'll have more clapping and cheering that fat mess if the cameras flash him up on the big screen.
The media will immediately churn out the tired narrative of: "a few fans are protesting, but just listen to that support."
A far more effective protest is lobbing hundreds/thousands of tennis balls on the pitch. The match would be stopped and It would take a fair while to clear them up, during which time prolonged chanting could take place. This chanting could be replaced immediately with vociferous support for the team (even if it's undeserved) as soon as the referee blows for a restart, leaving those in the directors box and the viewing worldwide audience who we're protesting against.
Fair play to the organisers like, but they have had 20+ years to plan and the best they can do is an unimaginative walk out that is going to be spun another way.
Everton, that.