50s court case ruled that denying tax-exemptions for constitutionally protected speech is unconstitutional. Idea of such tax rules are increasingly floated by democrats
1952 California denied tax exemptions to groups that advocated for overthrowing the US gov't. Court ruled that its the same as a fine
[A] discriminatory denial of a tax exemption for engaging in speech is a limitation on free speech…. To deny an exemption to claimants who engage in certain forms of speech is in effect to penalize them for such speech. Its deterrent effect is the same as if the State were to fine them for this speech.
Now, in 2019, Beto O'Rourke has publicly endorsed the view that "religious institutions, like colleges, churches, charities, should lose their tax-exempt status if they oppose same-sex marriage."