It's about as impenetrable as the idea of suicidal terrorism. What kind of rock would you have to live under to not know how incredibly addictive and dangerous it is? If all else about it were benign - the method of production alone would keep any sane person from getting near it. Merck, Pfizer, et. al. might make some errors once in a while, but the drugs cleared for productions are at least produced with six sigma levels of quality and security. Meth is made by those with a rudimentary knowledge of chemistry utilizing cleaning products mixed in a bathtub!
I was thinking about the image of a meth addict's teeth (or lack thereof as the case may be) when I visited my dentist a few months ago. I was almost going to ask if he had ever seen any examples of the rotted teeth that mark heavy duty users. But I realized that anyone using that stuff, to that degree, is not visiting the dentist.
I would be willing to take a live and let live stance on this if they were only killing themselves. The children, the increased health-care and law enforcement expenses - all of it is the classic example of letting externalities fall on the productive and responsible members of society. It aggravates me greatly.
They still try to see a dentist, but most dentists refuse to treat them, especially if the patient is on welfare. All they will do is pull all their teeth and give them dentures. I have known 15 year olds with disgusting meth mouth, who just can't face the idea of wearing dentures, so they go around with huge cavities visible.
Meth also causes psychotic episodes. We had a sixteen year old who was ordered to do service for a woman in restitution for a previous breaking and entry. The kid went over and the woman let him in and he raped and murdered her, dragged this 350 lb woman up a ladder to her loft, and strangled her with a vacuum cleaner cord. This kid would never have been able to do that under normal circumstances (straight).