There are 2 ways in which a person comes to the faith, and they need both.
1 is natural reason
2 supernatural reason
natural reason will create sympathy for the faith, and an adherence to the faith based on natural appetites
supernatrual reason will sustain natural reason, and will grow from natural reason, and will provide justification for remaining Catholic in spite of alternatives that also appeal.
Unless they be naturally inclined to agree with traditional values and the faith, they have no love of objective truth, but love instead subjective truth, and they will not change their mind, until some natural cause makes them change their love of subjective truth into the love of objective truth.
In circuмstances where it is not possible to convert someone using natural means, for example by conditioning their psychology to respect objective truths, then it is impossible.
Such people are lost in delirium, and this is a self imposed delirium, and they are damned by choice. Not knowing how to be virtueous, but knowing how to sin, they are lost.
One can preach the message of the gospel, but "he who has ears to hear let him hear", and he who does not, let him be to thee like a heathen and a publican, i.e anathema.
I dont see why Catholics should have to sit down with some faithless one and teach them the basics of objective truth and basic skills in interpreting reality. If they dont have these skills it is because they dont want them, i.e did not find them useful to accomplish their desires.
Hence their desires are evil, and they will get what they deserve.