The first and most evident is that the reason is false. That hosting provider makes it clear in its ToS that extremist groups aren't allowed, and when one is detected they actively ban those accounts. They've show documental proof of both.
The second is that it violates the first amendment of the US's own constitution, which uses universal language, not discriminating between citizens and non-citizens, nor between inside and outside US territories, nor between nationals and foreigners. So any federal US action trying to prevent people anywhere from saying anything they want between themselves, and with people in the US, is, in principle at least, out of bounds.
The first and most evident is that the reason is false. That hosting provider makes it clear in its ToS that extremist groups aren't allowed, and when one is detected they actively ban those accounts. They've show documental proof of both.
The second is that it violates the first amendment of the US's own constitution, which uses universal language, not discriminating between citizens and non-citizens, nor between inside and outside US territories, nor between nationals and foreigners. So any federal US action trying to prevent people anywhere from saying anything they want between themselves, and with people in the US, is, in principle at least, out of bounds.