There are a very few instances where people have been invited to join. Rebel has pegged this one. To be one you have to ask one to join. At least in the deep south here in Texas and Louisiana. The second part of your question as to why we have secrets. These are only so that one mason may know another mason in the dark of night as well as in the light of day. They are what we call the modes of recognition. All the rest I am able to talk about and have.
Freemasonry HAS NEVER AND WILL NEVER be associated with the KKK. PERIOD.
As far as the K.G.C. most the the founding fathers of that organization were Masons and borrowed from the the ritual rewritten to suit them. In a way that they could have there own deep and sometimes dark secrets. That is one of the reasons that I am searching for the writers of their ritual as I believe that it will contain information or clues to the K.G.C. treasure. Realize that there were many organizations that borrowed from the Masonic Fraternity their rituals. I have seen a copy of the ritual of the American Grange. It is almost the same as that of the masons. Why would the K.G.C. ritual end up in a Masonic Library simple, some one found a copy of the ritual in Gram pa's belongings along with his Masonic things not knowing what to do with them. They were given to the local lodge. The local lodge not knowing what to do with the K.G.C. ritual, past it along to the Grand Lodge Library and that is where it sits today. Somewhere!!!!
I was a secretary of my local lodge in Iowa for 10 years. In that time I don't know or can count how many times a family would come to me and deliver a box of Masonic items to me, not knowing exactly what to do with them after a family member had passed. I hauled boxes of Masonic item to the Grand Lodge Library and Museum some they were happy to receive some were sent back home to rest in the storage closet of our local lodge.
I hope that this answers some of your questions. Any others that I can answer I will.
Senior Deacon