Those who rejected the Trinity doctrine ​ — some of whom were later called Unitarians, as opposed to Trinitarians — ​ often became the object of intense persecution by Catholics and Protestants alike.
Neid, kes hülgasid kolmainuõpetuse (osa nimetati hiljem unitaarideks, vastandina trinitaaridele ehk kolmainuõpetuse pooldajatele), kiusasid katoliiklased ja protestandid sageli ägedalt taga.