I have crohn's colitis as well (it's definitely CD that I have since I have the perianal crohn's skin tags as well my CD was affecting my small intestine along with my colon and anal tags for the first 3 yrs when I first became sick so my DX is definitely CD)....I too found when I quit smoking that my CD turned even more horrible, I quit for 3 yrs and I started smoking again (I only smoke 6/day) and it definitely helped calm things down some.
It is true that it's the carbon monoxide that specifically aids with inflammation in the colon (which are basically the words from the researchers that discovered this, therefore it doesn't matter if the inflammation is from CD or UC.
Smoking is bad for CD in the small intestine but I have not had it affect my small intestines for the last 17 yrs and I've smoked through most of those 17 yrs....besides, we are all different and none of the research is necessarily written in stone either. Some CDers don't do any worse from smoking, while others do, just like not all UCers that smoke find relief either.
Apparently they're suppose to be working on a med that mimics what carbon monoxide from smoking does to help relieve inflammation in the colon, until then I will continue to smoke...my doc already confirmed to me that a mere 6 smokes a day is no different or worse than the pollution/poisons we breath in daily from our environment anyway.
I certainly am not trying to promote smoking because it is bad overall for you, I'm just sharing my experiances with it/without it.