I was a smoker for 6 years and have been on both sides of the exchange, and I'm OP's side.

Withdrawal sucks, but it isn't life-threatening, so I fail to see how the onus should be on the people around the smoker to put up with the consequences of smoking rather than the one who chooses to smoke. People need to deal with their habits and hobbies in a way that doesn't inconvenience those around them. If they fail to do that, then they're an asshole.

Smokers have options to get the nic fix. They can chew gum, they can use a patch, they can vape. All of them can give a smoker the nic they need without making them unpleasant to be around, and 2 of them can even be using during the trip if one isn't enough.

Smokers have options. Choosing not avail one's self of those options is a dick move.