Yes, in the same way tobacco is. If Tobacco was discovered now it would be class A, no question. Beer was only invented by monks because the water was undrinkable, but booze kills thousands a year, either directly or indirectly. Just because both are legal doesn't mean Dope should be, Its been very well manipulated under the guise of 'medicinal'. Oh bingo, we'll sell it now under medicinal even if it isn't. Cynical marketing, much?
We've tried it before (prohibition on alcohol) and the results were disastrous. If there is a linkage between marijuana use and hard drugs it is more likely because in order to get marijuana here (at least until recently) was from drug dealers who also might trade in stronger drugs with a higher profit margin and want to escalate their customers to those products. And once you get 'into the system' say for a pot bust now you have a criminal record. Good luck on your job seeking and what jobs are open to you? Drug dealing or committing theft etc. Clearly more damage is done by alcohol and tobacco (of course more people use it but due to cultural reasons I don't see that going away anytime soon, though smoking rates have dropped it seems. But those addicts can often lead 'productive' lives and can 'function' in society because it is acceptable.) But you are right that simply because legal drugs are bad doesn't mean illegal ones are good. But:
1) likely you can't eliminate addiction or use so the question is try to mitigate the harmful effects. A legal market, at least for some with age limits etc, would at least make drugs more stable or pure and customers (and doctors) would know what a person was using. Not like with these synthetics or homemade meth causing chaos in places. Think of bootleg moonshine verses a government sanctioned bottled-in-bond whiskey.
2) other countries have decriminalized or even legalized and they have less drug use across the board than the US or UK (Portugal comes to mind etc) and this also could, if done in larger countries, take out the cartels and turn it into a stable, orderly business with less violence.
3) some people are just fucked and likely will never be able to quit. Should we kill them like Philippians or Indonesia, throw them into and out of prison and allow to commit more and more crime, like the USA, or try to treat them medically or even allow them to 'shoot up' at a government facility to curb their urges and give them 'beer money' for sweeping the streets like Amsterdam is doing? Less property and violent crime should be the goal.