The maxim, "a government of laws, not of men" means state power should be exercised according to consistent principles and policy even beyond the letter of the law, not at the whim of bureaucrats or even leadership. Because it's generally impossible to draft laws to enumerate every possible scenario, contingency, and condition, statutes tend to nominally grant powers broader than for the purposes intended, even when there's no intent for them to be applied beyond the original purpose. For practical and procedural reasons courts typically only safeguard this principle by looking to whether the law nominally grants a power to do something, rather than if the power is rightfully exercised under a more wholistic and detailed interpretation of the laws, but the principle is still enshrined in US organic law, and in jurisprudence generally. Courts often do scrutinize exercises of state power to determine whether they violate this principle, but which applications are scrutinized tend to be a function of contemporary political debates and a courts ideological makeup.

These deportations are an interesting study in how this plays out, because historically immigration and, especially, deportations is an area of law where the usual rule pertains. But free speech is the complete opposite, where for the past 100 years courts are much more scrutinizing; indeed, precedent in free speech case law requires explicit, deliberate, and fine-grained application of varying levels of scrutiny in each, individual case, a process which is quite exceptional even in cases involving constitutional powers and rights.

It's worth pointing out that prior to the modern legal era, free speech law was quite different, both nationally and at the state level. Regulations and applications of regulations that incidentally impinged upon speech, but which otherwise clearly derived from legitimate state powers, received very light of any scrutiny. Regulation of commercial activity, for example, usually would not be considered to violate free speech rights even if it prohibited certain speech outright, so long as enforcement was nominally directed at commercial activity per se.

I don't pretend to be a lawyer, but I'm pretty sure that revoking a visa is not a criminal sanction, and the Dept of State has broad discretion wrt visas.

The person who wrote the article was at a protest. I presume he was identified as being there via his cell phone. Then, being a visa holder, he was investigated for being a security risk. He evidently was not deemed to be one, his visa was not revoked, and he was not charged with anything.

BTW, I'd be spooked, too, if federal agents arrived at my door to question me.