In this specific situation, it's probably not ethically neutral but I think a sensible path would be to say to Current Friend, "I know you might not have picked up on it, but Former Friend and I have drifted apart since January 6th 2021 due to political differences." There's a lot of subtext there, but it doesn't explicitly hit the details of what kind of Terrible FF has drifted into. And then feel your way towards whether Current Friend wants more details about that, or whether that's more than CF wanted to know.