In the antebellum south, the Klan did not exist, because there was no need for it to exist, as long as blacks were held in abject servitude, enslavement, and legally classified as property. However, the south chose to rebel against the National Government and thereby setup their own confederate government in rebellion against the national union of the States. The south lost that war, the slaves became emancipated, and the passage of the 13th, 14th, and 15th Amendments provided those that previously were held in servitude, with equal justice, voting rights, and the due process of the law; in short, all the rights that all citizens of this country are equally entitled to. Of course, there is the law as written, and then there is the law as applied, and those southerners that were still alive but defeated in the south, took it upon themselves, to create what became to be known as the Klan, of which its expressed primary purpose was to terrorize those that previously were enslaved, so as to maintain the supremacy of those that called themselves "white", as well as to pervert equality and justice, by taking the law into their own hands by their guns, and doing so, by any means, necessary.
The National Government through its legislative branch, did reply to the uprising of the Klan, by passing, not one but three different Enforcement Acts in 1870 and 1871, specifically to address the intimidation and disregard of Constitutional rights that blacks as well as other citizens were subjected to, while living in the south. Further to the point, this government looked upon the Klan, as an active terrorist rebellion that needed to be crushed, and thereupon through its legislation made it clear that the utilization of the armed forces of this National Government was not only appropriate against the Klan when they were found to be violating the rights of inhabitants, but that the suspension of the writ of habeas corpus as well as martial law was permitted, if necessary, to fully combat the Klan terrorism.
Later, the effectiveness of these Enforcement Acts was mitigated by Supreme Court decisions as well as northern indifference, which is one of the significant reasons why the Klan, and those that represent the ideology of the Klan, are still relevant and still terrorizing people today. The fact is it is a disappointing regression that today the Klan is still able to propagate its hate, and intimidation, under the protection of their First Amendment Constitutional rights, when in action and actuality, the Klan clearly crosses into domestic acts of terrorism, again and again.
The Klan, its adherents, and organizations that are similar to the Klan, must be seen as for what they are: domestic terrorist organizations. All the laws that are necessary to effectively deal with the Klan already exist, and thereby the only thing that needs to be done is to execute those laws against the Klan and its members, without giving any quarter, again and again. The Klan was born from the frustration of first losing at the Presidential ballot box, then by resorting to the gun of war and losing there, and finally by losing the southern way of life through the passage of new Constitutional Amendments after the Civil war. However, their smoldering ignorant ideological hatred still exists, today, and still terrorizes innocent civilians.
Thus, for the sake of the innocent, as well as for the sake of the country that is the last best hope on earth, the Klan must never ride again.