Christian Nationalism is bad though. I mean mutilating children is also bad, anyone who supports circumcision has a wild and poor understanding of the scripture.
Why should Christians be against Christian nationalists? If you oppose the idea of Islamic theocracies then why be such a hypocrite? The idea of nation is a spiritual one. Jesus did not force his religion onto others, he showed them the light through reason, compassion, and sacrifice.
We were built on the idea of the separation of Church and State. (Even though it was never fully realized. But I hope it will be one day.) The American value that all men are created equal is not just a spiritual one but a moral one separate from ones religion. The many people who convert to Christianity do so because of the accepting Christians who do not persecute those of other beliefs. And I often feel those who are shamed or bullied into Christianity, or out of fear of damnation learn and read the scriptures for all the wrong reasons.
Separation of church and state means separation from the Catholic church, not separation from religion. Aka actual Protestantism
There is no logical argument against Christian Nationalism that isn't just hating Christianity. It solves every problem. Circumcision is Jewish.