Jennifer - I suppose you could choose to read the character according to however one likes. And like Ueshiba, you could choose to reframe "so" as love, just as he did with "ai." Furthermore, not having access to my dictionaries, I don't know how "so" has been used in other words. But in Araki-ryu and Jikishinkage-ryu, the two schools which I'm aware of that use the word, "soshin," it is simply a means to more effectively manipulate, control, and most likely kill your enemy.
I suppose this somehow leads to 'all is fair in love and war' in the long run.
Realizing that this is also an independent interpetation.