This is factually false, cannabis is addictive and you do experience withdrawal if you stop using it after habitual long term use (anxiety, depression, among other withdrawal symptoms).
I'm not saying this is an argument for making it illegal, caffeine is physically addictive and certainly you experience withdrawal if you stop using it suddenly, etc.
However, saying cannabis is not addictive at all is just propaganda. If any chemical does something measurable in your body, you will almost certainly experience withdrawal symptoms if you suddenly stop using it after long term use. Withdrawal symptoms being unpleasant is basically the definition of physical addiction.
I think the addictive vs. non-addictive debate is mostly about what people mean by the word "addictive." Clinically, you're right: anything that affects the dopamine system will have clinically addictive properties (i.e. bingeing, preoccupation, anxiety, etc), and there's plenty of clinical research showing that long-term cannabis use can result in addiction. But what people sometimes mean by "addictive" is physically-painful and/or physically-dangerous withdrawal symptoms: nauseau, migraines, shaking, or even potentially death in the case of alcohol. Even heavy cannabis use doesn't generally result in those kinds of withdrawal symptoms.
Cannabis is very much psychologically addictive and hence the word pothead. If you don't know the pot culture and you don't see how these people can't have fun or pass a day without pot you will change your mind