Firstly, it is not infallible, as it is addressed "To Our Beloved Sons the Cardinals of the Holy Roman Church and to Our Venerable Brothers the Archbishops and Bishops of the Austrian Empire."
Secondly, he reaffirmed the dogma without exception in #4, "There is only one true, holy, Catholic church, which is the Apostolic Roman Church. There is only one See founded in Peter by the word of the Lord,[3] outside of which we cannot find either true faith or eternal salvation."
Thirdly, he was addressing and condemning those who embraced rationalism, as from #6 and the beginning of #7, "These are the people whom the Church seeks to bring back to sound reasoning." He was condemning those who knowingly rejected Catholicism, thereby rejected the grace of God and sinned against the faith, that they have no hope of salvation whatsoever, the same type of people Our Lord condemns: "Whoever does not believe will be condemned," in contrast with those who are in ignorance beyond control and have not sinned in that regard, perhaps one day they might be lead to know and embrace the faith. Further, there's no indication that they will be saved in the state they are.
But it's a horrible statement which he should not have made in the first place.