It depends. There are ways to disagree. There are ways to move in other directions. Formally, though, if the pope demands obedience of an individual or group, including censure and/or excommunication (which was at play at one point for the SSPX, as well as the now-reconciled FSSP branch)... you do what the pope says.

Mentally, I always go back to St. Teresa of Avila: "St. Teresa knew in her heart that the visions were truly from Christ, yet out of obedience she performed the gesture when the Lord next appeared [context: her confessor had told her to make a rude "fig" gesture to the apparition of Christ, the equivalent of flicking Jesus off, because he believed her visions to be from the Evil One.] She did so with great interior distress and while silently apologizing to Jesus. Far from being offended, Christ reassured her and praised her obedience, telling her (in essence) that she had done the right thing by obeying her confessor."

Even though the confessor was wrong.

Or Msgr. Rosetti, just this week, getting ousted as exorcist of the Archdiocese of Washington for speculating openly as to whether "aliens" might in fact be demonic representations. ++McElroy is clearly acting unjustly. But Msgr. Rosetti's response:

“I believe it is of the utmost importance to be obedient to the Church and I will continue to endeavor to subject all that I do and the Center to be thus obedient,” he said in his response.

“I will continue to encourage all to do so as well,” the priest said. Referring to a symbol of unity with the Catholic Church, he added, “As I often say: ‘Stay in the Boat!’, that is, stay in the barque of Peter, it will lead you safely home.”

SSPX is out of the boat. And while I don't wish them ill, it won't surprise me when they drown.