Smoking causes cancer. That is a proven fact, known for decades. Moreover, secondhand smoke causes cancer. It is not right for anyone to spew carcinogenic particles into the air that other people breathe.
As a matter of public health and safety, to extend lives, improve livelihoods, and preemptively avoid expensive medical treatments, we should ban smoking in public. For similar and even more pressing reasons, we should ban smoking near children, including in buildings that children live in or frequent.
Alternatives are available for nicotine addicts. They are welcome to use a patch, chew or ingest their drug, or even use a vaporizer as long as it does not put toxic chemicals in the air that other people breathe. We will all be better off when smoking is entirely banned in public.