It’s possible the folks pictured haven’t been to LES and/or don’t make it to many games, period.
Maybe they’re used to small venues where there’s enough room that people don’t have to sit behind them.
Maybe they’re oblivious to the impact on others.
Maybe they are in fact inconsiderate jerks.
Don’t be jerks.
I doubt that any of us is 100% perfect over time in our behavior at games, where you’re often crammed together with strangers in an emotional and not entirely physically comfortable environment. But the chair issue is almost entirely fixable via policy.
Where we cannot apparently behave with regard to others concerning stadium chairs, I’m good with a ban at this point. Other stadiums do similar stuff. There are existing rules that apparently aren’t enforced. Create cheap alternatives to bringing one’s own chairs, and make the change.