Please stay with the topic, or debate this somewhere else, thank you.
That subreddit is not religious in nature, even though it is frequented with Christians. The reasons given for why one might want to pursue the sub’s goal are all secular. So I don’t know if it’d help to add something that Catholicism logically demands.
Those people who are not our valid spouse are our siblings, and that means if you’re a man then any lust for a woman is lusting for your own sister. And if our Catholic sisters are our real sisters, and so lusting for them is fundamentally incestuous, then there is no justification either for lusting after women who are not our Catholic sisters either.
We are all family, and so all lust is incestuous desire for your sister. It is the root of incest, it is one of the reasons that Pope St. Gregory characterized lust as a capital or deadly sin, because it leads to other sins, and if we do not lust, then incest adultery and all other fornication will not happen either, since lust is the ‘head’ of those sins.
So in direct answer to the OP, I would warn other members of the sub to ‘keep it secular,’ and if they don’t abide by that, then try to interject something distinctively Catholic into the discussion, like what I outlined above, rather than go into a theological topic that is not apparently relevant, such as differences in soteriology.
Thank you for keeping me on the straight and narrow path.
