Amandil is not assuming. Their comments are grounded in the constant teaching of the Church.
Not only is it grounded in Church teaching it’s grounded in reality and common sense.
This is something that oldcelt should find readily observable: sin is addictive.
Alcoholics steeped in their addiction deny their addiction exists.
If you asked them they would insist that they could give up alcohol any time they wanted.
Yet when it comes to the point of actually doing it, they either refuse ir simply can’t. Some are so deep into dependency that they can’t function without it.
People addicted to narcotics such as pot, cocaine, crack, or heroin are even worse. Aside from the obvious physical dependency and that they know that it’s killing them yet they
will not to be without it.
People who are in habitual sin, even if it is something like gambling or gossip, have so handed their wills over to the sin which they love that they simply have no will of their own in the matter. This is precisely what Jesus meant when He said, "those who sin make themselves slaves to sin. "
The deception of sin is so dangerous because it is precisely so subtle. Aside from the jolt reaction one has when one sins, the heightened fear and anxiety combined with excitement and lust for the object desired, once the deed is done and the emotions subside it’s easy to be fooled into the assumption, “well I don’t feel any different, it must not be sinful.”
This deception leads people to a further deception that sin is “no big deal”, that “it doesn’t hurt anyone”, that “it’s a victimless crime”, or “their doing what they love, what’s so wrong with that”(sound familiar?).
“Live and let live,” is Satan’s perfect ad campaign. Because as Lewis put it in letter 12 from “The Screwtape Letters”:
“Because indeed the safest road to hell is the gradual one-soft under foot, without any sudden turns, without milestones, without signposts…”