"Urine and the back country have gone together forever too. Can I walk up and p!ss on your leg while you're smoking a cigar? May $hit in your shoe?" - Kevin smith
Sorry, but your analogy is invalid. A better analogy would be me doing my best to go off trail and out of sight to take a wiz, but am unknowingly in view of another section of trail, and am unaware of your approach. Then you proceed to throw a hissy fit because you didn't come to the woods to see a guy with his junk hanging out.
The only way your analogy is valid is if someone sat next to you on the side of the trail, lit up and blew smoke in your face. I think even smokers would agree that is out of line and is not likely to happen.
If you don't like the smoke then pass them or move somewhere else. If 2 minutes of residual smoke smell is going to ruin 3 days in the wilderness, then you have some issues that can only be cured by a conversation on a couch...
Chris Scala wrote a great post on the last page, btw. Worth reading.