Some years ago I had long and interesting conversations with a member (not the one holding the menkyo kaiden) of the German shibu of the KSR. And it became very clear, that the ban of aikidoka in the KSR shibu is founded in the teachings of the ryu. It seems to become evident when you practice long enough to understand what Frieday calls "the kabbala" of the ryu: The inner teachings, the "ura" doctrine.
Whether it is true that there is such a deep gap between the inner teachings of KSR and aikido I am not able to judge.
Okay so nobody in Kashima Shinryu trains Aikido, yet they understand Aikido so well
that they know they don't want new students who practice Aikido. But that should come as no surprise since the ban against aikidoka is built into the okuden of the ryu - so they've obviously banned aikidoka from training for hundreds of years before Aikido ever existed!
Sorry, this just gets sillier and sillier to me. It makes more and more sense, though, particularly if Tissier's teachings are as widespread as you say, that at some point the ryu decided that the Aikido organizations posed a real threat to the proper continuation of their art. They don't want to be invited to Aikido seminars, they don't want people coming to train and then showing their friends at the Aikido dojo stuff they don't understand yet, etc. Presumably other arts don't pose as much of a threat in that regard because they are not open-ended like Aikido is.
Sorry for the argumentativeness, Carsten - it's not you I am arguing with, its this omote cultishness that seems to impy that Aikido training damages someone's budo permanently.