Essentially correct. Roblox has a sort of central platform, the basic stuff which determines how interacting works, how things can look, what defines objects etc, and then it has things that run on top of that, so specific games with rules, different experiences within that base platform.

For example, you may want to play a spiderman kind of webslinging game. The rules for shooting your web and attaching to buildings along with how swinging works are all handled by the custom code, but the core of how the game looks, multiplayer conections, state saving, and so on are all handled by the outer game logic.

So all these people dressing as ice agents may be running around in other peoples games and using in game capabilities to block them from moving, to harass them, and to grief them. The other players can ban the ICE agent players from their game but is is exhausting and the disruption is real.

The more shared spaces, the large public rooms, is where you would do something like protest. You could take all the players who are griefing with ICE outfits and make it clear they are not welcome, unpopular, and just plain annoying. It may or may not work, but it is good the kids are not just accepting it and moving on. The kids are all right.