Shalom Rabbi, I thought I should offer this: Franz Rosenzweig, in Part II, Book 3 of the Star of Redemption, makes an allusive, elliptical remark to the effect that the mitzvah of loving one’s fellow as oneself contains within it, on a subtextual level, a commandment to believe that one’s fellow is like oneself. The mitzvah itself thus precludes the use of ‘it’ in relation to human beings. The same is true of mitzvot relating to Hashem (on the basic level of personhood). This subtextual element in Hashem’s Word is established in and through the Primordial World (as elucidated in Franz Rosenzweig’s philosophy) and is therefore not explicitly stated in halakhos / Hashem’s Word.
‘Dark horse’ Franz may be, but hashkafically he’s got this sewn up.
EDIT: A snippet from The Star, as a taster:
‘For man’s act of love is only apparently an act. It is not said to him by G-d to do unto his neighbour what he would like done to himself. This practical form of the commandment of love of the neighbour, serving as a rule of conduct, really only designates the lower negative limit; the commandment forbids crossing over this limit of action, and already for this reason alone, it will be better to express it, even outwardly, in a negative form. For man must love his neighbour as himself. Like himself. Your neighbour is ‘like you’. Man must not deny himself. Precisely here, in this commandment of love of the neighbour, his Self is finally definitively con-firmed in its place. The world is not put before his eyes like a vast mixture, and he is not told, with a finger pointing at all this mixture: ‘This is what you are. This is what you are - so stop demarcating yourself from it, enter into it, disappear in it, keep on until you lose yourself in it.’ No, quite the contrary: out of the infinite chaos of the world, a neighbour, his neighbour, is placed before his soul, and of him, to begin with exclusively of him, he is told: he is like you. ‘Like you’, hence not ‘you’. You remain You and you will remain You. But he will not remain a He for you and hence only a This for Your You; no, he is like you, like your You, a You like you, an I - a soul.’
(P.257 of Barbara Galli’s English translation of The Star of Redemption.)
I could go on about Franz and his work, but I don’t want to overload the answer box here. As for Franz’s sources, he talks about his method in his work - which includes a commitment to ‘non-fanatical’ hashkafah (no derogatory meaning intended by him with this term), that attempts to put hashkafah on a different footing from those that require an ‘auctoritas’ (if you will pardon the expression) other than the existence, the witness, of Israel herself. I’ll say no more for now. Blessings :)