Hence to purchase the books produced by SSPX and Angelus (however Catholic by content) is to subsidize schism because it keeps their presses going and their employees at work where they are also publishing and distributing schismatic work that undermines Holy Mother the Church. I would not have purchased perfectly accurate Bibles from Communist publishing houses nor Missals that might be printed by NAMBLA for similar reasons of moral obligation not to cooperate with other evils.
The behavior of Lefebvre and his co-conspirators has put him, them and their organizations beyond the pale until they first take care of the basic business of surrendering to papal authority, retracting their nearly two decades of character assassination of John Paul II, retracting their anti-Catholic cafeteria views, apologizing to those whom they have duped and to whom they have lied, publicly and unconditionally pleading for forgiveness and mercy by the Holy See, and publicly performing appropriate and hopefully drastic penance.
But, hey, that is just me, speaking from the experience of the actual tradition of my upbringing in 1950s Catholicism. If B-16 is more charitable towards the schism, then who am I to disagree? Until B-16 says otherwise, my preference is for the full measure of richly deserved punishment of SSPX, its excommunicated leaders and its schismatic adherents as a condition of the restoration of those still alive to Catholicism in good standing.
Using your logic, no one should give any money to the numerous dioceses in the US that support CCPA, by bringing their priests over here to say mass and go to our seminaries why real Catholics in China are being murdered and tortured. I'm all for that.