The only evidence i need to disprove these things in my mind are the facts:
1. I have asthma (admittedly mild) and I use my inhalor about half as often when Im regularly getting stoned.
2. I live in a pretty cold environment (my room in the basement can get pretty cold in the winter) and I'm almost never sick.

I also love that they cited a member of the DuPont family as a source. Yeah he's got noooo reason to keep cannabis illegal. :P

I think most people just disregard this type of propaganda, and those that believe it just wind up looking kinda stupid when they compare notes with an actually informed person.