In modern American discourse, the term "Civil Rights" refers to the activism around the 1960's. The stuff in the 1860s is referred to as "Civil War" or "Abolitionism" or "Reconstruction" etc. I, for one, had never heard of the Civil Rights Act of 1866 until reading your post there - it's not part of the lexicon. When Americans refer to "The Civil Rights Act" they are referring to the Civil Rights Act of 1964:
http://en.wikipedia.org/wiki/Civil_Rights_Act_of_1964
"Civil rights activism" generally would cover everything from the American Revolution (which was all about the civil right of voting) to the present (gay equality, etc.). I see no particular reason that anyone would understand "Civil Rights activism" (in America) to refer specifically to the Civil War era. Indeed, I strongly suspect that you turned up the 1866 Act as a post-hoc justification for your initial gaffe.
I think I mentioned earlier that I wondered about the Irish element after realising that the Irish immigrants escaping famine and the civil rights activism were only a few years apart. I posted a picture in the South African thread to show the 100 years between the beginning of the civil rights activism and the civil rights era.
If I was referring to the civil rights era, I would have said civil rights era.
My exact words were:
You may be right, but I haven't looked at the early supporters of black civil right activists so I am also clueless here. It was just something that occured to me when I realised the timeline of Irish immigration preceded the civil rights movement by just a few years especially the immigrants who fled the famine