when somebody says "i'm not a christian", that doesn't only mean that they don't believe in angels and demons, or trinities, or zombies, or cannibalism.

it also means that they reject the christian value system.

of course, there are varying levels of rejection, and what that means is complicated. but, the key to understanding an atheist is removing yourself from the framework of christianity, first. it's very hard to understand the irreligious when you've spent your entire life chained in the cave of religion.

so, for something like drug addiction, a christian is going to frame the issue in terms of a value system that upholds hard work, and rejects sloth as a sin. a christian would consequently consider addiction as a "sinful" lifestyle that is rebellious, because it rejects "god". this would then be contrasted with a pious lifestyle. somebody that upholds sobriety would consequently be godly, in their rejection of sinfulness.

i've repeatedly ranted against the protestant work ethic and upheld sloth as a virtue.

but, this entire discussion exists within the framework of christianity itself, and the aim of an atheist is to reject this. a humanist would not care about what somebody might imagine that god would think of the scenario. an atheist does not believe in concepts of sin, and so does not interpret drug use or promiscuity through a filter of rebelliousness or sinfulness, but rather seeks to rationalize it by empirically analyzing it's effects on the individual's health.

so, where a christian may be tempted to certain behaviours as rebellious and sinful, because the issue was framed that way to them, an atheist is likely to flatly reject such behaviours as irrational and harmful to one's health - which is why the christians framed them that way in the first place.

this is why religion is so damaging to a healthy society, and why it is so important to rationalize away these concepts of "sin" and "rebellion", as they manufacture stupidity, rather than abolish it.

somebody rebelling against religion may consequently see an atheist and a religious conservative as somewhat equivalent, because they're telling them the same thing about their destructive behaviour. but, the truth here is that the reason this is happening is because rebellion is irrational - and the true thing to learn from this is that rebels are idiots.