First of all, let me say that I am not a smoker. Never have been.
There's no disputing, with all the data available these days, that tobacco smoke is neither good for a body, whether it is first-hand or second-hand.
Having said that, you'll probably get the argument from many about smoking and the environment - and rightly so. You have to view it in relative terms.
Obviously, the exhaust from cars and factories, for example, would be more collectively harmful to the evironment than a stadium full of smokers, just by the sheer volume of smoke. You also need to take into account greenhouse gases from things like coal-fired plants.
It would be difficult to scientifically measure how much harm tobacco smoke is actually doing to the environment, but no doubt there is some
, but negligible compared to all others available.
Now, it's debateable as to how much harm tobacco smoke is doing to the environment, but, speaking personally, what I find quite objectionable is the smell of the smoke. It's not just tobacco smoke, but also the smoke of marijuana and barbecues (especially with briquettes).
Again, for the volume of smoke that a barbecue can potentially produce, one could argue that the smoke from these devices is much more harmful than tobacco smoking.
... Millions of cigarette butts are discarded onto the ground every day. ...
As for leftover cigarette butts in the environment, I have no idea as to this harm in the soil. I imagine with all the chemicals in tobacco, there would potentially be some harm, but would it be as bad as plastic bags, for example?