You know that when a dictionary calls a definition of a word "archaic", they mean "no longer correct", right? Using "litigate" to simply mean "argue against" or "dispute" is to confusingly misuse the word.

> when a dictionary calls a definition of a word "archaic", they mean "no longer correct",

I just checked a few dictionary definitions of 'archaic' and none of them say anything about no longer being correct.

OED lists as:

    > Belonging to an earlier period, no longer in common use,
    > though still retained either by individuals, or
    > generally, for special purposes, poetical, liturgical

If "no longer in common use" or "for special purposes" doesn't mean incorrect in an entirely consensus-driven language, what does? It gives a motivating example of "obleege", for oblige, which I note my spell-checker has helpfully underlined in red.

Nothing about 'not common' or 'special purposes' implies 'incorrect'. There are many perfectly good words and phrases in English that are not commonly used or are only used for special purposes, but that in no way makes them incorrect.