well tsuwm's knowledge of Yiddish is most likely better than mine, and since i tend to contribute from work (where i have no need of a shelf of reference book on language, even if i want to carry all of them in to the office!) I am hazzarding a guess.
-- that "schmatitude " is a made up word-- and like many other expressions is doubled rhymed pair. (zig- zag, rollie -pollie, eeny-meeny) for emphisis. the "schm" has a nice yiddish feel to it-- and the right sound value..

So-- yes, it's just an idiom-- an emphatic way of saying "I don't care what you think--do it any way" .


my other obsession