Certainly not all of them. For example, the House sponsor of the immigration bill that serves as the foundation of our current immigration system was Albert Johnson, R-WA, supporter of eugenics and purported member of the Klan. The Senate sponsor wasn't a Klansman, just a guy who greatly admired Mussolini in the 30s (and a Republican as well).
The pre-Civil Rights era Dixiecrats are today's pro-Trump Southern Republicans. Strom Thurmond began the trend when he flipped from the Democratic party to the Republican party in 1964 in response to Lyndon Johnson's support of the Civil Rights Act of 1964 and it wasn't the first time Strom pulled a similar stunt. In 1948 he ran for the president on the Dixiecrat ticket (formal name of the party was the States Rights Party) in a response to a pro-civil rights plank in the platform of the National Democratic Party. Jeff Sessions the first Republican Senator to endorse Trump when the Donald was running in the Republican primaries in 2016 started his political career in Alabama as Dixiecrat type Southern Democrat. Same for Roy Moore and Jessie Helms (in NC). As far as Byrd was concerned he was a Klansman in 1946 and voted against all of the civil rights bills in the '60s. By the '80s he had become a pro-Civil Rights Democrat and even received an award from the NAACP.
Absolutely. Most people make an honest effort to be open minded and equitable though. Other people run political campaigns based so entirely on racist lies, designed solely to establish differences with an Other, that they've sunk to nationally claiming that immigrants are eating pets. Still other people cast votes to be president for the racist liar.