Ofcourse, if the Church had dogmatically declared  Water Baptism and the teaching on the Immaculate Conception before Aquinas made those comments, then obviously Aquinas would have rejected BoD and accepted the Church's teaching on the Immaculate Conception.

 

My mistake. Actually Water Baptism was infallibly declared before Aquinas made such comments, but that does not mean that he knew of those teachings.

St. Robert Bellarmine: “It is very credible that St. Thomas, Alexander of Hales, and other scholastic doctors had not seen the second synod of Nice [Nicea II], nor the eighth general synod… [they] were long in obscurity, and were first published in our own age, as may be known from their not being extant in the older volumes of the councils; and St. Thomas and the other ancient schoolmen never make any mention of this Nicene Synod.” (De Imag. Sanct. Lib. II. Cap. Xxij.; quoted in NPNF2, Vol. 14, p. 526)

St. Robert Bellarmine says that St. Thomas Aquinas was probably unaware of what was taught in the seventh and eighth ecuмenical councils of the Catholic Church: that is, the Second Council of Nicea in 787, and the Fourth Council of Constantinople in 869-870. This is a significant statement. Some people have argued that it’s impossible or unthinkable that a doctor of the Church could be wrong or ignorant of something taught at a council. To the contrary, the teaching of doctors of the Church is important, but it is not infallible. A doctor of the Church can be wrong and even ignorant of certain things that have been taught by the Church. Their teaching certainly does not weigh more than the teaching of the Magisterium.

Pope Benedict XIV, Apostolica (# 6), June 26, 1749: “The Church’s judgment is preferable to that of a Doctor renowned for his holiness and teaching.”

Pope Pius XII, Humani generis (# 21), Aug. 12, 1950: “This deposit of faith our Divine Redeemer has given for authentic interpretation not to each of the faithful, not even to theologians, but only to the Teaching Authority of the Church.’”

So we can see that the defenders of “baptism of desire”– and even those who say that it’s unthinkable that baptism of desire could be incompatible with Catholic teaching if a doctor of the Church believed in it – are wrong again