Yeah, there are just a lot of unattractive qualities about smoking.
First, it’s dangerous for those around you. This includes loved ones and strangers. Second hand smoke is harmful, so people are reproachful.
Second, the smell really gets to a lot of people. People don’t like it around smoking areas, but it can be hard to deal with even when you are just in close proximity with a smoker, if you are really averse to it. Working out can positively impact your health, but people still don’t like folks who just walk around with body odor. People react negatively to the smell of alcohol too. There is no demographic on earth that just walks around reeking that distinctly all day long. There are individuals, but no other demographic. I mean, maybe homeless people, but then the stench is more varied and less distinct.
Third, smokers often cause inconvenience to those around them. Smoke breaks slow down everything, and they can get quite frequent depending on who you are dealing with. Constantly having to wait for someone to smoke can be irritating, especially since there is rarely a way for them to repay the favor.
Fourth, smoking is considered dirty. This is for a variety of reasons, not the least of which being the smell. Also, all of the anti-tobacco propaganda (especially that in schools) focuses on the tar and nasty that builds up in your chest. Because of this image, many consider smokers dirty as well.
Fifth, no one else gets to/has to live by their vices quite as strictly. Drinkers have to keep their drinking to nights and weekends. Same with pot smokers. Cigarette smokers not only want to smoke every hour or so, they expect to.
Sixth, cigarette smokers are often self-righteous. This one is unfortunate, because it is a direct response to the way they are treated. However, all of the pressure has made a lot of smokers into self-righteous douche bags who are always on a rant about how their “right” to smoke has been abridged.
These are just a few. I mean, I hang out with plenty of smokers, so I don’t adhere to most of these. You asked why people are rude though, and that would be my guess as to why.