Smokers don’t seem to be under any illusions about whether it’s bad for them? When people have conflicting desires, I think what even counts as “self-interest” gets complicated. Often people are acting at cross-purposes to some of their desires.

Now you have weakened the generalization to the point it's meaningless.

What act exactly do people believe to be in their self-interest? Why are you claiming it's the anti-social ones and not the pro-social if the believe is not rooted on reality?