My Southern grandmother, born during Reconstruction, was a yellow dog Democrat (despite being quite conservative and a teetotaler). She only voted other than for the Democrat twice in her life: against Al Smith in 1928 ("damned wet Catholic" in her words) and against Kennedy in 1960. (She would not say whether she voted for the Republican or some third party candidate - only that she had split her ticket and voted against Smith and Kennedy)
I have uncles who have huge issues with the Catholic faith.
I come from a long line of Anabaptists who were treated very badly during the 15th century.
Today I think most of them know some Catholics and have come to the realization that Catholics aren’t so bad. But the prejudices are still out there.