My opinion that PI is not a place for kids is not entirely based on the theory that kids shouldn't be exposed to the behavior of people who drink too much or the theory that kids would be better off in a more kid-friendly environment and/or getting more rest (though I do agree with these thoughts). My opinion is also based on the level of enjoyment adults, who are visiting PI without children, should expect to get out of their evening. Please note that I'm not trying to offend anyone with my opinions...
Disney, like most companies, sets certain expectations for their customers. For example, when I visit a non-Disney "fancy" restaurant, and pay high dinner prices, I expect to be able to dine in an atmosphere free of children being loud and boisterous. In Epcot though, when I dine at the fairly expensive Le Cellier, I expect that I'll encounter children who are having fun, and yes, sometimes crying out of tiredness; after all, Epcot is a place for families.
When I go to PI, an area marketed to adults, the expectation is not that I'll have to dodge kids who are running around while their parents are dancing or watching the band. Nor is it that I will encounter children interfering with my ability to hear the performers at the Adventurers Club. I also don't expect to be made to feel uncomfortable sitting next to a child, no matter how well-behaved, when a somewhat adult joke is told. I have experienced all of the above and I don't believe this is the atmosphere Disney was originally trying to create at PI.
As noted in my earlier post, I think Disney needs to make up its mind as to what PI's target audience is and then stick to an appropriate range of offerings. Then, we'll all know what to expect and can choose to visit or not.