I did use pure nicotine and it was very bad for my health, probably due to high dosage, but still.
I've used heavy stimulants, benzos, opioids, dissociatives without an issue, but nicotine is in a class of its own in terms of how insidiously addictive it is.
But just from a health point of view: extreme arm and hand joint issues, forearm vascular issues that made my hands numb at night, palpitations/arrithmia like I was about to die when I used nicotine before sleep and I was drifting to sleep -- it really felt like I was about to die, like my heart was mangled up.
A lot of people consume nicotine. It has been isolated and used in products for a long time. There's no clear link to cancer, but it could impact cardiovascular health (like all stimulants seem to).
Some research indicates that nicotine can influence how existing cancer behaves and spreads, so that's worth considering.
He was suggesting— jokingly— that maybe coffee cancels out the deleterious effects of smoking, because indeed coffee + a cigar or pipe is truly an excellent experience.