“Democrats? ALL of them?”
Nom not all of them as there were Southern Republicans who opposed the Civil Rights Acts.
I suppose “all” is a bit sweeping. But there weren’t a whole lot of Republican politicians in office down South until the Dems switched over to the other side.
OK. Name one Southern Republican Senator that opposed the Civil Rights legislation. I will make this easy for you. There weren’t any. Period. There not even any Southern Republican political office holders at the time. From Virginia to Texas, it was all Dems all the time.