I think one will be hard pressed to suggest that there were no Christian influences in the thinking of Onisaburo. But, first, another question: Why connect "The Japanese Spirit" to "Love"? I'm not sure I understand how that was first connected in your post. If you wouldn't mind, could you also explain this a bit more - please/thanks.
As an example, upon my first reading of the Doka's and other spiritual philosophical writings by O'Sensei I didn't read them in the context or culture of which they were written. The context I used was that of my own. Now over-time and with some help of college education of Japanese culture that familiarize me more with the Japanese, beyond dojo manners and the common Japanese words and phrases used in the dojo, I make an effort to place what O'Sensei said in its native context. Part of that effort is making connections that are available from where O'Sensei drew from and was inspired from.
I don't think that I can any longer substitute my native context for the original context. I may not be able to completely read O'Sensei in the full proper context, and this is better than relying on my context as a substitute . But what I don't want to do is to make any substitutions of my own, especially if I have accesses to the original context, at any degree. If there is no context or complete context originally in what O'Sensei said, then it is better to have none at all.
Because, I feel, then you are not fleshing the words with the proper context and if you do that then your result is inaccurate, and misleading subject to anyone's and everyone's own personal interpretation. WOW how confusing is that to hear a million different people purporting and their interpretations, all screaming know what he meant. So at least if we can go back to the root sources like Onisaburo, Budo culture, and in that time period of O'Sensei's which all played a major role in what O'Sensei was saying at least gives us a change at the Turkey Shoot with ol' Bess Brown.