Everyone reacts differently, and few really know what is in their medicine and what the long term effects of smoking/vaping these fertilizers/toxins/etc really are. Some have allergic reactions (to varying degrees) to cannabis. Many, many others can make themselves blow chunks simply by giving something enough power.
That being said, I have rarely heard such misinformed, subjective rationalization. Just because the sky is blue and I vape doesn't mean that my vaping makes the sky blue. Correlation vs cause and effect. You cannot logically look at 1 aspect of your life (cannabis uptake) w/o considering every other influencing factor to the condition. For example: "well, I actually stopped and started drinking coffee concurrently w/ cannabis uptake", or: "I was vaping a lot when stressed, and nauseous. Once I stopped being stressed so much I didn't need to vape, and was no longer nauseous". Did the vaping make you nauseous? Or the stress? Or something else altogether?
Many people, including myself use cannabis for its antiemetic properties. I have late stage chronic pancreatitis. When I was younger, I would be hospitalized 3-4 times a year for around 2 weeks at a stretch. As far back as 30 years ago, the drs would call my wife out into the hall and tell her she needed to say her goodbyes, as I probably wouldn't see the morning. Since being able to consume the quantities I need, by growing for myself, I have decreased my need to be hospitalized - from several times a year, to once a year, to today where it has been almost 7 years since hospitalization. Far from cured, but have been able to keep attacks below the level requiring hospitalization. Unlike CHS, cannabis' antiemetic properties are well documented.
To accomplish this required massive uptake of cannabis utilizing it's natural anti-nausea benefits. I typically use 1-3 grams a day, and have for 20 years.
I also think that a lot of this 'speculation' is disinformation, intentional or not, that furthers the stand of cannabis opponents and detracts from actual benefits the plant provides.
If someone is 'addicted' to mj, it has very little to do w/ mj and everything to do w/ themselves. I would sure miss dinner if I had to go w/o it - am I addicted to dinner? Sorry if this isn't compassionate enough, but I'm tired of a plant being blamed for some peoples lack of character. If your mind is such that you can become 'addicted' (negative connotations implied) to mj, you should probably never touch it - as well as: coffee, sugar, candy, porn, heavy cream sauces, video games and much more.