Is Marijuana a bad drug? Yes. Is alcohol a bad drug? Yes. Anybody who says otherwise is being untruthful. However, if a person were to review the behaviors of people under the influence of both drugs it is arguable that those using marijuana are less of a danger. In general marijuana use does not lead to violence...yes there are certainly exceptions but ask any cop out there and most fights involve drunk people...not stoners.
Should we as a society say that one drug is OK while the other is not? Both drugs are bad, no question. But the effects of fighting the "drug war" are worse. Loss of civil liberties, loss of property rights, loss of innocent lives in the various turf wars. And the expenditure of billions of dollars that at the end of the year has accomplished nothing.
I firmly believe that the criminal misuse of drugs should be heavily punished, if you drive drunk or stoned the punishments should be very onerous. If you harm or kill someone the perpetrator should be tried for the serious crimes that those are.
However, if a person wants to get drunk or stoned in their own home and no one else is involved (save for those who wish to partake) who are we to tell them no? The Declaration of Independance says very clearly "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness."
If a person derives their happiness by being drunk or stoned it is not up to us to deny them their basic human right to do so. And in the interest of full disclosure I have never been either drunk or stoned in my entire life, so whatever they do will have zero effect on me.