“Why would anyone one assume that marijuana is safer than alcohol or cigarettes? “
One would not assume that, but the actual evidence is clear that it does not cause the social and physical harm that alcohol and cigarettes cause.
“isnt it addictive?”
Not in the same way that alcohol or cigarettes are, or even heroin or cocaine are. Millions of people have quit smoking marijuana with little struggle.
” Does smoking it have less an effect on the lungs than tobacco? And it’s usually not even filtered?”
Filters don’t prevent the damage to ones health that smoking causes. And while in theory a marijuana cigarette can be as bad as a tobacco cigarette, it is extremely rare for a pothead to smoke 30 marijuana cigarettes a day!
“As far as I know, there is no other purpose to smoking marijuana other than to get high, an altered mental status”
Actually there is now a lot of evidence for marijuana having numerous medical uses, and it is safer to smoke a marijuana cigarette than to take the active ingredient in pill form.
I absolutely do not support smoking marijuana to get high. A college roommate of mine flunked out because he was high all semester. But discussions should be grounded in fact, and the anti-marijuana folks are fact-impaired.