The Birchers got themselves in a pickle when they opposed the Civil Rights Movement in the 60’s, not because of rights per se, but because they claimed the movement was full of communists in leadership positions. To this day their main cause is the fight against the spread of communism and socialism
They were correct. Martin King was a commie, or at least a pinko sympathizer. Why haven't the FBI files been released? He's been dead almost 50 years. Inquiring minds want to know!
There's a little more to it than that. I'm no fan of the "civil rights movement," but the Birch Society was always a coalition of radical libertarians and traditional white Southern segregationists, and the latter very much considered "race mixing" to be the essence of Communism. Each side of this coalition was given free reign and for the most part ignored each other's "eccentricities." At any rate, white racialism was definitely a factor, along with the Communists in the civil rights movement.
Another factor was that, like Goldwater, the non-racialists in the Society considered all federal involvement in civil rights issues to be illegitimate and contrary to true Constitutional federalism. I pretty much agree with this position, but unfortunately the racialists in the organization (and in the conservative movement) simply refused to let their "blood is thicker than water" concept go. It's a darn shame that these issues could not have been addressed at local and state levels. It was a case of an unstoppable force meeting an immovable object.