This is a question that I’ve had over the years, and have noticed this time and time again.
Let’s say someone comes to this forum, or any Christian forum for that matter, and says, “I am a Jew/Muslim/Buddhist/Hindu, whatever”. They are usually treated far nicer and with more respect than if they were to come to a religious Christian forum and say, “I am a Jew/Muslim/Buddhist/Hindu” but I used to be a born again Christian/Catholic".
IOW why are they treated nicer if they were never part of your religion at all, than if they once were and joined another?
Because, if they were Catholic, unless and until they repent, they are committing what is most likely mortal sin… Apostasy. It’s grievous matter, and if they were confirmed Catholic, they were most likely taught that, and they made their choice willingly in the vast majority of cases.
Further, most of those former catholics seem to come specifically to covert others away from the church. They are worse than a wolf in the sheep… their eternal fate is described as being better were they to tie an anchor stone about their neck and dive in the dead sea than take one from the fold.
Me, I try to pray for them. But they usually come specifically to violate the rules. And I can’t speak for others, but I usually try to avoid responding, and instead, when they start the anti-catholic polemic, report them.
For the other ex-christians, the fate is similar, and the rationale, usually, as well. If they accept and then reject Christ, until they repent that, they go straight to hell at death, or so it is taught.
Still, even they are in dire need of reconversion. If they come in search, we truly must do what we can to aid them back to Truth.
The lifelong non-Christian, however, has a slim glimmer of possibility of heaven, due to invincible ignorance, or unconquerable obstacles. (Being a woman in a muslim village, for example, is likely an unconquerable obstacle, and they can hope only for the baptism of desire. If they found enough to know the formula, they could even baptize.)