O Sensei himself - and both the following doshu aswell - expressively stated aikido to be open for all person, from which religion or spiritual tradition ever they may come.
I don't understand how this can be applied by a 'Christian': for the character of Christ is described as a pacifist - turn the other cheek, etc., whereas aikido is concerned with, as you say, 'stopping weapons'. So aikido is only open to you insofar as your pre-existing beliefs don't clash with those inherent in aikido.
I know that most Christians don't actually follow the teachings of 'Christ', so it's a bit stupid of me to bring it up....
Sorry for the off-topic-ish comment: it's just something that has been bugging me since I saw the 'Can Christians do Aikido?' thread. Carry on.