the same could be said about the smoke from a cars muffler, or the smoke from a BBQ grill, or drinking in excess (driving or not), or the garbage we throw on the ground everyday that make it to our water source
Yes people dropping litter on the ground should be banned, because, as with smoking, it is creating a negative externality (that is, a market failure which the free market cannot effectively address itself). The harm to the person who drops that garbage is far less than the harm done to them along with the harm done to everyone else. Hence the optimal choice for that individual is unlikely to be in society's best interests. So, you ban it, and have the rubbish desposed of in the best way possible for society (e.g. people pay taxes, and in return a rubbish collection service is provided which will take all your rubbish and dispose of it).
As for drinking, if you drink excessively around other people, you don't harm them. You may harm them as a result of drinking excessively, but then that is illegal. With smoking if you smoke around other people, you harm them. Hence it too should be illegal (unless the damage done is so inconsequential that it's not worth worrying about, and that certainly isn't the case with smoking!). Similarly if you drink excessively and drive a car, you're no longer properly in control of it, and are highly likely to hurt someone else other than yourself, hence that too is illegal.
The smoke from a BBQ grill is typically released outside, and hence will dissipate without causing any meaningful damage to others. I'm all for a ban on very smoky BBQ grills inside where there is a lack of ventilation such that the health of employees and customers will be adversely affected.
As for legalisation of some drugs, again what people do to their own bodies is their choice. So long as they're not hurting others, and are given the full information so they can make an informed decision about whether to hurt themselves or not, I don't see the issue.
Ultimately people should have the right to harm themselves if they want to, but should not have the right to harm others, and that's what the smoking ban is about - by all means smoke where you won't hurt others, and just yourself, but don't smoke where you will hurt other people.