Public espousal of views that are not permitted in the workplace by the government puts one’s employer at financial risk.
It’s evidence that one has those views (so it’s circumstantial evidence that one may have expressed them at work), and- worse- circumstantial evidence that the employer knew of them.
That puts the employer behind the eightball if a EEOC or civil charge is made against them. If you don't like the circumvention of First Amendment rights blame the EEOC, not me. Government regulates workplace speech and behavior.