Sorry for sounding nit-picky, I didn't want to undermine your argument as I agree with you.
The only problem I find is that, even if 1) and 2) are true, and you are talking to someone in group 2), it doesn't entail that the person believes that "1) is true". They still may be perfectly self-consistent by rejecting 1).
Talking just from my experience (anecdotal evidence, I know) most people from the group 2) would reject 1). People don't know the scientific studies or do not trust them enough to be convinced.
That's fair enough, and I agree, people can be very reluctant on that front.
It goes against a lot of conditioning that drugs are just plain bad, and it appears to contradict their lived experience in which they don't think they've really had an issue with alcohol so it must be OK. Not like those other things where people get addicted and get into all sorts of trouble. It's just a beer. Never mind aunt Theresa who died falling down the stairs, drunk as a skunk, at the age of 40 because her cirrhotic liver just burst like an overripe melon when she hit the bottom step. Or your friend's mum who they're not on speaking terms with because she put her drinking habit ahead of feeding her kids when she was young. If anything that just adds to the conviction that drugs must be so much worse, because drugs are bad, and this is 'just' a beer.
Personally I have a complex relationship with alcohol. I brew at home but I'm not blind to the damage it's done to me (thankfully just some pretty bad hangovers and behaving like an arse from time to time, well, and the belly) or to others.
The only problem I find is that, even if 1) and 2) are true, and you are talking to someone in group 2), it doesn't entail that the person believes that "1) is true". They still may be perfectly self-consistent by rejecting 1).
Talking just from my experience (anecdotal evidence, I know) most people from the group 2) would reject 1). People don't know the scientific studies or do not trust them enough to be convinced.