I don't think anyone has encouraged the use of marijuana but rather the legalization of it. The reason for this is marijuana prohibition is extremely counterproductive as well as extraordinarily wasteful and damaging to the social order.
But cigarette use is discouraged because, while marijuana is non-addictive and relatively benign, cigarettes are more addictive than heroin and are potentially lethal.
More addictive then heroine is an asinine statement. It is one of the hardest to kick because it is everywhere but it is not more addictive then heroine, a drug that can kill you if you quit too quickly.
You are spot on with the statement " The reason for this is marijuana prohibition is extremely counterproductive as well as extraordinarily wasteful and damaging to the social order" though.
In all honesty, the contention that we are discouraging smoking but legalizing pot would be encouraging pot is a misnomer. We would not be encouraging pot any more than we would be encouraging cigarettes as they would (and are in some places) both legal. The reality is that we would be taking one step forward in treating them both the same with simple indifference. If you want to smoke, go ahead. If you want to toke, go ahead. Personally, I don't see any reason that the 2 substances should be treated any differently at all.