The rejection of fanaticism went out the door along with E Pluribus Unum in the 50's when the Christian nationalists forced their religion on the national motto. Then over the next decade black people were lynched and attacked with fire hoses when they were asking for basic rights.
They also started conversion camps where they emotionally and sometimes physically and secually abuse minors in conversion camps to attempt to change sexual orientation.
I believe it was Nixon who helped foem fox News to pull the Republicans further right and we've been seeing the consequences of that.
Basically the fanaticism has always been there, but with the internet and social media, it's easier for them to make their voice heard.