1. southern democrats were the bane of the real democrats, everyone knows that. Out-and-out racists like Wallace and Maddox were not welcome into the democrat caucus. Cripes, Wallace even ran for the Presidence against a bona fide democrat. Maddox railed at civil rights with an axe. Not JKF-like;<quoted text>
It was JfO, but with republicans pushing through the passage against the will of many democrats, but there were democrats that voted for it as well. The Civil Rights Act was passed with robust debate from both parties, and support and opponents from both parties, and was not rammed through with a simple majority at midnight on Christmas. If the southern democrats could have shut down the government over that bill to stop it dead in it's tracks, they would have done so.
2. You wrote : "If the southern democrats could have shut down the government over that bill to stop it dead in it's tracks, they would have done so.". How can you be so sure? I can be sure that Cruz and the Tea Party closed down the gov't, but not so certain about the Southern Dems in 1964.