Because they didn't. Why would they have? The Democrats were the party filibustering the civil rights act. And multiple pro-segregation Democrats are STILL in office and also still Democrats... Joe Biden is one of them.

Yes, but should not we leave that identification process to the person reading the source? Because the problem is in your first sentence... who is "we?" I'm fine if the "we" is just us people, deciding for ourselves. If "we" is some chosen entity, then I'm not.

That'd be unfair, too. Discussion of ALL topics should be allowed. Because who decides what is a valid source?