My big argument is THE BIG PICTURE.
If the SSPX is making lots of SMALL moves, ALL OF WHICH tend toward ONE CLEAR GOAL -- then they are all part of a bigger plan.
Just like if I steal $10 from a man every day for a year, I actually stole $3650, which is a tidy sum. You have to look at that big picture.
For example:
* We're just going to work closer with the Novus Ordo Bishops, focus on how they are the Ordinary and have more communication with them, bring them into the seminary to speak with the seminarians, and have the seminarians kneel and kiss their ring.
* We're just going to start teaching Theology in English.
* We're just going to make Tradition more palatable to non-Catholics, we are now allergic to being called "weird", "rad trad", "extremist", "disobedient", etc.
* We're just going to have a table-like altar
* We're just going to have Novus Ordo priests witness SSPX marriages
* We're just going to totally change the seminary formation process, including the spiritual formation: making OBEDIENCE the highest virtue (as opposed to a more appropriate virtue for soldiers during a time of war, such as Prudence, Fortitude, Fidelity, etc.)
(see Sean Johnson's book for dozens more such changes WHICH HAVE HAPPENED, PAST TENSE)
You can't excuse ALL of these in toto, even if you might brush each of them aside individually with a lame or even a good excuse.