Sports players are in many ways political representatives of their nation to an extent that it can be warranted to treat them as such. It’s not likely they have anything against the individuals (at least not all of them) on the team, but refusing to extend sports etiquette to your opponents in a match like this shows that you don’t respect the nation or their current actions. In one sense, people are powerless against a mob of their peers. But in another, ‘Americans’ voted for Trump without obviously visible voter suppression (not saying it doesn’t exist, but you can’t expect someone from another country to understand the nuances of gerrymandering, voter ID laws, etc). While it would feel bad personally, its completely understandable to me why someone may be treated differently when the nation they currently represent is a fascist or genocidal one. If enough people cared, they could stop their nation, but at the cost to their own safety and comfort.