The principle is that nobody should be forced to employ somebody they don't want to employ.
Right to be one's own boss: it is called freedom. It doesn't have to be written in the constitution with those exact words. I don't think the US is a socialist country just yet.
And your narrative of letting people self-organize seems wrong. There were laws mandating segregation. That is not self-organization, but government interference.
Obviously murdering people and burning down businesses is and should be illegal.