It's worth pointing out that it was never impossible to be drunk (or encounter drunk people) inside Disneyland even if most people couldn't buy alcohol there.
Even before DCA, the park had a number of establishments across the street and a monorail to a hotel where alcohol was freely available. And, of course, Club 33 and (way, way back) Holidayland.
I think the other castle parks have shown that incorporating alcohol at table service restaurants, and only table service restaurants, has not had an appreciable negative effect on the atmosphere while adding to Disney's bottom line in a way that does not exclude other people, nor does it result in cuts.
So I think it's a win-win for 99% of guests.
Maybe I've been very lucky, but in the 20 years I've been going to parks, the only place I've ever encountered belligerent, obnoxious drunks has been one time at Knott's Scary Farm. And theme park drinks, as has been said, are typically expensive enough to ward off a lot of the worst behavior people tend to assume happens when alcohol becomes available.