LOL! This reminds me of the anti-drug speeches we used to get back in grade school. In those presentations, every drug (heroin, cocaine, marijuana, speed, downers, alcohol) was the same (BAD!!!!!!!), because even if a drug wasn't dangerously addictive, it was a "gateway drug" based on the logic above.
Sure - you start with one or two drinks, but soon that won't be enough. Soon, you'll want 4 or 5. And - then - your body will want something stronger, like marijuana - and it will be the same cycle. Then - once you're hooked on marijuana, your body will want cocaine - and so on.
As I look back on this, I am stunned that they used to tell us this crap. Hell - I drink beer all the time. Sometimes, I will have 4 or 5, but usually it is one or two. It's refreshing - especially after playing ball for 2 or 3 hours. I am still waiting for the day though, when my body/brain says to me "This beer isn't enough - give me some marijuana!!!!!!!!"
The "progression" logic is just so flawed.