There have been studies linking just about any outcome to any behaviour, anyone with enough money has ever wanted.
Myself I like to err on the side of caution, since my country has free healthcare which means I have to pay for the mistakes of others, so I don't want them making mistakes in the first place. They should feel free to smoke all the weed they want and become psychotic drones in the fucking Congo
Everything has some risk, and the anecdotal evidence is that weed does not affect the vast majority of adults in a way that would result in additional healthcare needs.
No. They are generally safe and people NEED to get around to live. They don't NEED to get high though.
>cycling also be banned? How about alcohol?
Yes, definitely. Both things are risky and bad. But that would be hard to achieve. Since weed has never been legal (at least here), things can go on the way they are.