Ouch this is embarrassing --- Look, I was going through a weird stage with the whole yoga pants thing...and the Ipad, well I was caught up in a Walking Dead watching marathon on Netflix and to say I was addicted is putting it mildly....
In all seriousness, that is a major bummer, when you drop that kind of coin and you end up caught up in someone else's "This is my vacation I paid for it and I'm going to do WHATEVER I want" world....but really I think it being "Disney" signature restaurant and it being a "Disney" resort is the issue here.
It's hard for Disney to enforce even the simplest of rules when you don't ever want to offend anyone and you're trying to make the whole world happy.
Look I'm a pretty liberal guy, but there is nothing wrong with enforcing a simple set of rules to make everyone's experience a WHOLE lot better. I'm in typical theme park clothes during the day at the parks, but I'm always in a collared shirt when we hit or TS dinners. It's not that hard to do a simple polo devoid of stains and some khaki shorts or non ripped jeans and you've already upped your game up. If someone has a problem with that, then they're not the kind of people that you would want in your 'Signature' establishment anyway.
For the record our experiences there were devoid of those type of characters. In fact the first time we went there was only 2 tables within eye shot that had children at it (our kids were 6 and 10 then), our kids rarely acted up at dinner but if they did, it was draw straws and one of us takes the kid outside to handle the situation -- The last time we were there we were sat in area where it was entirely all couples except for one other party of 4 (besides us) and no kids in site. We have a couple of teenagers now and as stuck as they are to their phones, we don't allow it at the dinner table.
It's unfortunate that ability to follow a few common courtesies these days is not so common.
Anyway bummer on the YS for you brother. I know it wouldn't take much more than that for me to take my business elsewhere so I get it. I do want to try Shula's one time, I've heard nothing but good about that joint.