The phrase "questionable logic" is just a tad oxymoronic, doncha think?
I mean, if it's questionable, then perhaps it was never logic of any sort.
(I get your larger point, of course. But because you are somebody who preaches in favor of clear expression, maybe you could come up with a better term?)
I agree, the addition of the questionable shoots down the possibility of logic. It’s just a gentler way of saying so.