It might be their attitude or their inability to keep a civil tongue in their heads or their incessant carping and complaining against the pope or their invention of non-existent "crises" to justify their defiance or disobedience or impudence. Maybe it's the willingness to put words in the pope's mouth as to foreign policy matters or to accept the AP's alleged paraphrase whose accuracy the Vatican denies. Maybe, just maybe, they are not getting the shaft or even one tenth of the punishment they deserve. Protestants, Jews, Muslims and Buddhists make no claim to be Catholic. The pope has no obligation to accommodate the enemy within.
Here is how to distinguish your ancestors from SSPX. Your ancestors were probably not in the habit of vilifying (not just disagreeing with/not just criticizing) the pope. Your ancestors probably did not take pride in disobeying the pope. In the event that they did any of these things, the fact that they were your ancestors does not insulate them from the consequences and they knew that.
Finally, God is love. Therefore, God is charity (another word for love). Yet God is just and he sends some whom He loves to hell because they have insisted on such justice by their behavior. It is not uncharitable to refuse to indulge the fiction that SSPXers claim when they claim to be Catholics while rejecting the authority of the Church itself. It is charitable to insist that they accept the unvarnished truth or the truth with the bark on.
St. Augustine calls obedience the greatest of virtues.
St. Teresa declares that no path leads so quickly to the summit of perfection as the path of obedience.
"Learn to comply willingly with the wishes of thy equals, and thus thou wilt learn to fulfil cheerfully the commands of thy superiors."-St. Francis de Sales.
"The greater thou art, the more humble thyself in all things, and thou shalt find grace before God: for great is the power of God alone, and He is honored by the humble."-Ecclesiaticus
"Take away self-will, and there will no longer be any hell."-St. Bernard