I'm not a lawyer, but I don't expect this to be a a "hill to die on" at all.
If this professor is unconnected to the sanctioned Tornado Cash service, then Github shouldn't have to worry about running afoul of the sanctions by hosting the code.
Because privacy is important and the elimination of it has been a huge part of most totalitarian regimes. Why wouldn’t you die on the hill?
This isn't about privacy, it's about free speech as stated above. He wants to make the code public, not keep it in private.
It's about privacy, free speech is just the legal justification for being able to publish the content