Are you seriously claiming that inhaling smoke from burning vegetation isn’t bad for your health?
That would depend. Is there tar in the smoke resultant of the burn? Is that tar absorbable by the alveoli, or does it build up over time, thus impeding oxygen absorption?
Are there active ingredients (chemicals) in the smoke? On par, are they vasodialative or vasoconstrictive? The first lowers blood pressure, the latter spikes it.
So if you have high blood pressure and you smoke a plant that directly applies a vasodilator to the lungs' alveoli, it lowers you blood pressure. If the tars are 98% absorbable by the lungs, then it just gets flushed out with your other waste, and leaves no scarring or damage.
So if someone has hypertension and high blood-pressure, smoking a vasodilative plant can be quite beneficial.
More to the point, one needn't "smoke" anything. This substance can be eaten, vaporized with heat, and/or absorbed directly through the dermis.
So your all encompassing generalization is aught but food for fact-starved fools. You can surely do better.