I don't do it, and I don't like it.
It's particularly inconsiderate to me when people do it in outdoor places with lots of others nearby. This isn't just something that poisons the one doing it. If it were, like alcohol, I wouldn't find it as irritating. As someone with a very sensitive nose, I find that smell maddening. It just sticks to everything, and it will not go away. Honestly, I wish it didn't exist. The thought of large businesses making money off of poisoning others is... very disturbing and says a lot about the darker parts of humanity.
Also, I don't really blame the smokers so much as I blame society for inventing such a horrible thing. If you smoke, it was your decision to start, and I'm aware of that. But I'm also aware that it can be very addictive and isn't quite your fault if you continue to do so. These people have my sympathies. I try not to judge them, and I try not to preach. It's sad, but like many horrible things in this world, it's here to stay. All I can really do is avoid them because I just can't stand the activity itself.