The difference there is Joe is an activist of non addictive substances. He chooses to associate his name with these things, some random guy just came out of left field and told us that Mike is an adderall addict, if Mike had said it then it would be different.
Addiction is a horrible thing and if Mike is suffering from it then I wish him all the best but I seriously question the motive of the starter of this rumour, they obviously didn't have Mike's best interests in mind.
Maybe he's a mate of Mike's and Mike doesn't mind? He might just be facing up to his demons, although I share the skepticism.
And weed IS addictive. The only people who say it isn't addictive are people who smoke weed on a regular basis. "I can give up at any time", somehow this phrase isn't tarred with the same brush as it is when uttered by an alchoholic.