Well, I think the point here (aside from the posts about alcoholism which is not what is being discussed, although it ALWAYS comes up in any discussion of the MK's alcohol policy) is that alcohol is not sold in the MK. Actually you are not allowed to bring your own alcohol into ANY Disney theme park, even the ones that sell it. If you're caught with it it will at the bare minimum be confiscated. If you argue with whoever catches you or raise a fuss I would think you risk expulsion from the park. That won't make for a fun day at the happiest place on earth for the party or their children. Not sure it matters WHY the guy wants to bring it into the park.
Not sure what the argument about whether or not people should drink alcohol at all is about.