They are purposefully obfuscating the issue by repeating the mantra "free speech." Even foreigners have constitutional rights when in US jurisdiction, but those rights are a lot more malleable when they intersect with other areas over which the executive has sovereignty. Like immigration, foreign affairs, and the military. The Supreme Court has been clear about this for a long, long time. Even in the most recent decision by the Court about the guy in El Salvador, if you actually read it, the Court says that the District Court has to treat the executive with great deference in this area.
The left is just ignoring that and screaming "free speech!" But any actual thought would tell you that's retarded. Does al-Qaeda get to send immigrant "refugees" to distribute pamphlets encouraging people to become terrorists? Did the Soviet Union get to send agents into America to advocate for the overthrow of capitalism? Does the DPRK get to send people to America to encourage joining the DPRK military and fighting the West? No, of course not. But by the left's current logic, all of that should be protected by the First Amendment.
If you're American and want to incite anti-American hate, then you can do that within the bounds of the law. But if you're a foreigner, you can't. That's both morally and legally correct.