Over on another forum, the argument was given that legitimately promulgated doesn't mean licit.

Neo-SSPXers defense of Fellay and co. is tantamount to the neotrads and neocats defense of VII and the new mass. They have to deny objective reality in order to hold their position. "Subsistit in doesn't mean 'subsits in!'" Liberals. Pathetic.
Bingo. I wish I could think of another example - where one word introduces a whole can of worms of objectionable statements. I was once told that 'subsistit in' meant the same thing as 'est' which even I, never the most proficient Latinist, can spot the error in. 'Legitimately promulgated' is rubbish, as if the New Mass is a) valid (which it is) and b) licit (which it ain't, as the Church can't promulgate anything sinful) then logically c) the New Mass is not sinful.
A single word destroys the whole reason there is such a thing as the SSPX - if traditionalism was just a sentimental attachment to the old Mass because it's pretty, and the New Mass was as good, then the hardest deal Rome made would be preferable to where the Resistance is now.
If the New Mass legitimately promulgated, then it's equal to the Tridentine. Then there is no crisis in the Church (ooh! ooh! Those nice Council Fathers were only
misinterpreted, just as Saint Benedict XVI says!) and you and I might as well link arms and dance into the nearest NO Church and effusively praise Paul VI.