First, I know what most of you are going to say. I myself was an internet atheist 20 years ago, quoting Dawkins and Sagan at magic-sky-daddy believers. But this isn't about convincing anyone to believe.
This is about pragmatics. And, pragmatically, the single biggest enemy right now is the conservative Christian right. Anything to fracture that coalition benefits the left.
Luckily, their gospels are pretty left-wing. So, I offer for your consideration, the Christian angle.
I encourage those of you who went to Sunday school to brush up on your Scripture. Matthew is a treasure trove. When you're talking to someone on the right, start hitting them with chapter and verse.
If nothing else, this is initially shocking. They're supposed to be the Christians, and you're some filthy commie reminding them that Jesus called the wealthy priests hypocrites, and told us to feed the hungry and aid the sick.
They have defense mechanisms against your crybaby commie talk. They don't have defense mechanisms against their own scripture. At worst, you shake them loose from their script and confuse them, giving you openings for gentle deprogramming.
At best, they might reflect on their leadership and how closely they follow Jesus' commands. Anyone who really believes in him and really reads the gospels is going to wind up a leftist, whether they call it that or not.
Just food for thought. Read up on what Jesus said, use that against the people who claim to follow him. You don't have to believe yourself to recognize a powerful rhetorical tool.
You're not taking about christians, though, you're talking about Christian MAGA specifically; the christians who can understand that Trump is incompatible with their faith aren't the ones following him. What I'm saying is that their belief system isn't the opening you think it is with that crowd. They're basically Christian nationalists. One of the hallmarks of MAGA is that nothing is sacred to them. They will burn anything and anyone at the gross stale-McDonalds-smelling altar of their orange idol: Their parents, spouses, children, even their Lord and Saviour Jesus and the values in his book. They actively call their scripture weakness and think it was written by "the libruls".
Then call them a Jesus-hating heretic and move on. For someone like that, the best you can do is plant a seed of cognitive dissonance in their core beliefs.