There seems to be broad discretion that the government has in revoking visas.
Similarly, the US government can revoke someone's visa, but they can't revoke someone's visa because of speech protected by the first amendment.
It's a guest pass.
When getting a visa you're basically asked to agree to America's terms of service. Violations can be found pretty easily in the fine print if someone is really looking.
From there it's the same administrative work to revoke and deport as it is to say ban someone from Twitch for saying the wrong thing.