And that is true. But the way this storyline is going, it's more like Punk is a recovering alcoholic. If this feud was against someone who had problems with substance abuse themselves (like a Shawn Michaels, for example) it'd make a TON more sense.
I understand that in wrestling you have to suspend your disbelief. I have no problem when Kane has the ability to control fire (but apparently has the moral compass to not just shoot fireballs at people at the start of every match). That's fine to me. But when you are trying to make a storyline that's rooted in reality that makes giant leaps of logic, I have a problem with it. If he were to start drinking, is CM Punk more likely to become an alcholic and crave the stuff? Absolutely. But does he already crave it? No. Is the fact that his father was an alcoholic mean that (after 33 years of not drinking) Punk is more susceptible to dive into drinking after a tough loss? Nope. He's actually probably less likely.