Appropriation is bullshit, cultures should be allowed to freely copy from and imitate each other without restriction.
I think we just have a case of spoiled Americans that want to be the world's police.
Is it the shared language and the ease of communication?
There is Hollywood and most of stuff in internet in English is written by people form the states.
But then there is also the U.S. geopolitical and economical hegemony. People copycat everything american hoping that magically some of that success would stick too.
Results are weird. Some people advocate saving tap water here in Finland. Despite our country having very large number of lakes and swamps and no foreseeable shortage of water.
Analogy: Let's say you take a free intro taekwondo class. They outfit you with a white belt, obviously. But you think the red/black belt looks cool, so you start wearing that instead - maybe not in the dojang even, but just around town. You don't think martial artists should have a problem with that, maybe even challenge you to a fight? And even non-martial-artists shouldn't think you're kind of a poser?
If you walk around in army uniform and have never been in the army, you will invite criticism or even a kick in the butt. If you dress up as a nun or as a priest you are an impostor. If you decide it's cool to wear the "Ring of O" on your right hand, you'll invite some inconvenient misunderstandings - especially as a woman.
Everyone should be aware of societal codes and either obey them or live with the resulting misunderstandings. Shrugging your shoulders and violating those codes makes you a not nice person at worst, but casting this in "oppressive west vs. the rest" terms just muddies the water.
No they shouldn't. It in no ways diminishes the value or meaning of a red/black belt in taekwondo.
However, if they were to insist that practitioners treated them as if they'd earned the belt or, conversely, somehow prevented a legitimate holder of the belt from wearing one then you have a case for grievance.