CathInfo.com

but even he says that one can be saved outside the Church, if through no fault of their own they have had no opportunity to enter it.

https://stevensperay.wordpress.com/2012/12/04/fr-michael-muller-c-s-s-r-taught-the-doctrine-of-baptism-of-desire/
"Q. What are we to think of the salvation of those who are out of the pale of the Church without any fault of theirs, and who never had any opportunity of knowing better?
A. Their inculpable ignorance will not save them; but if they fear God and live up to their conscience, God, in His infinite mercy, will furnish them with the necessary means of salvation, even so as to send, if needed, an angel to instruct them in the Catholic faith, rather than let them perish through inculpable ignorance.
Q. Is it then right for us to say that one who was not received into the Church before his death, is damned?
A. No.
Q. Why not?
A. Because we cannot know for certain what takes place between God and the soul at the awful moment of death.
Q. What do you mean by this?
A. I mean that God, in His infinite mercy, may enlighten, at the hour of death, one who is not yet a Catholic, so that he may see the truth of the Catholic faith, be truly sorry for his sins, and sincerely desire to die a good Catholic.
Q. What do we say of those who receive such an extraordinary grace, and die in this manner?
A. We say of them that they die united, at least, to the soul of the Catholic Church, and are saved.
Q. What, then, awaits all those who are out of the Catholic Church, and die without having received such an extraordinary grace at the hour of death?
A. Eternal damnation."

So Muller certainly takes a more hardline view than Garrigou/Fenton( and myself) but even he says that one can be saved outside the Church, if through no fault of their own they have had no opportunity to enter it. The key difference between Muller and Brownson is that Muller is a priest/theologian, and a respectable scholar. He doesn't need to be vitriolic to get his point across