We must at least presume, if not assume, that all non-Catholics are damned and work under that assumption for the salvation of their souls. Of course, we leave their eternal fate and judgment to that of the One and Triune God.
This is mostly correct. If a man has given no external sign of conversion to the Faith prior to death, then we must judge with moral certainty that he is lost.
Most canonists and theologians also teach children baptized in heretical sects become culpable for the heresies of their parents at around 14 years. After this age, in the external forum they are presumed to have lost that membership in the Church that they acquired in baptism. Likewise, children who have never been baptized are presumed to be culpable for infidelity shortly past the age of reason. The reason is that there must be some element of moral or physical impossibility for ignorance to be said to be invincible. Those who live among and around Christians, where the Church has been established, must be presumed to be culpably ignorant.
Although Feeneyism is a very regrettable error, I don't judge Feeneyites harshly because, pre-Vatican II, just about every lay Catholic perfectly understood this. And the fruits of conversions from the heretical sects were abundant. Whereas, since that time, the proper understanding of ignorance and culpability has been thrown into the greatest confusion. Ignorance of what a man is bound to know is a sin, as all the Doctors teach. Ignorance that can be removed by due diligence is not invincible, and must be presumed to be culpable.
Still, Bowler's mistake is no different from saying, "If penitents think perfect contrition is a possibility, they will never want to come to confession". Noting that Trent says the sacrament of penance is necessary for salvation just as baptism itself is necessary (which evidently means in fact or in desire), I want to ask Bowler, If the possibility that the sacramental effect of penance can be received in desire does not undermine the necessity of the actual reception of the sacrament as soon as that becomes possible, why should it do so in the case of baptism?