Congress has the power of the purse, Trump’s efforts at Executive usurpation notwithstanding.
But that significant separation of powers concern pales before the Bill of Rights.
Unconstitutional conditions doctrine basics: The government "may not deny a benefit to a person on a basis that infringes his constitutionally protected... freedom of speech." This stems from cases like Speiser v. Randall (1958), which struck down a loyalty oath requirement for a tax exemption as penalizing protected speech, and Perry v. Sindermann (1972), protecting a professor from retaliation for criticism even without formal tenure.
Limits on funding conditions for speech: The Court distinguishes between permissible conditions that define the scope of a government-funded program (e.g., Rust v. Sullivan, 1991, allowing restrictions on abortion counseling in federally funded family planning projects) and impermissible ones that leverage funds to control or suppress speech outside the program or impose viewpoint discrimination.
Universities (especially in their academic mission) function like limited public forums or marketplaces of ideas with strong academic freedom protections, making viewpoint-based speech restrictions particularly suspect. Conditions must be viewpoint-neutral and not overly coercive.
Academic freedom and university context: v. Board of Regents (1967) struck down loyalty oaths and vague "subversive" speech restrictions for university faculty, emphasizing that academic settings require robust free speech and that vagueness in speech rules chills protected expression. Sweezy v. New Hampshire (1957) and related cases affirm academic freedom as a "special concern of the First Amendment," protecting inquiry, teaching, and expression from undue government interference.
Healy v. James (1972) and Tinker v. Des Moines (1969) extend strong First Amendment protections to campus speech and association, rejecting efforts to suppress disfavored views.
Professor Patty Pinko gets to preach Communism on federal education funds.
Professor Harry Hitler doesn’t get to harass the Black and Jewish students on federal educational funds, nor do his students.
I suspect racial, religious and national origin harassment must be dealt with with similar vigor and methods.