Already Proto-Indo-European had first and second person pronouns, including the "I" vs. "me" distinction, try again. So do Uralic languages, which some argue forms a larger family with the Indo-European languages.

So your propaganda event would be, at the minimum, something like 7000 years in the past.

It's Japanese which is the odd one out in this regard and I'd rather say it's about a penchant for indirectness as well as hammering down nails which stick out, easier done when enforced in an impersonal manner. Not "I think you smell", standing behind your words, meaning what you say and saying what you mean, opening yourself to challenge, but a fuzzy, out-of-nowhere-and-everywhere, "there is a smell in the room". Btw what's the net result of your justice system, and what are the cultural factors that allow neglecting basic rights of the individual in favour of the collective?