I don't think "he was within his rights as a resort guest" to get nasty. I have vacationed at other hot spots, and generally speaking, you can always eat at your hotel as a last resort if you didn't make arrangements somewhere else.
But that ain't the way it is at Disney! And it sounds like they were told it ain't that way at Disney! Rather than bite the bullet and make some plans in advance, they resorted to bullying, and I think that's just really wrong.
Unfortunately, I've seen "pissed off guests" twice now at Disney hotels freaking out because they couldn't get a meal at "their resort." One was at Jiko last May. OMG, this woman was soooooo angry because she couldn't eat at her resort's nice restaurant. Now, I don't know if it was a lack of planning on her part or maybe the restaurant lost her ADR (she and the family were seriously dressed up), but she couldn't eat there and was making a huge scene. She kept saying, "I know you're booked, but this is my hotel, I'm staying here." We were standing outside by the little creek and we could hear her even outside. I know they didn't seat her there. They ended up finding another restaurant for her to go to somewhere else; I don't know where, but it was resolved with, "If you leave right now, you'll make it in time," and off she went.
We witnessed something similar at the 'Ohana breakfast in September. It was during
free dining, and the restaurants were packed!!! DH & I had just gotten in line for the check in, maybe one or two others behind us (strangers), and this lady came, got her family to sit/wait at some chairs, and she gets in line to check in. She was pretty frantic and visibly upset. She kept saying she was late, she was late. The folks in front of us said they were running a few minutes late, too, but as long as you have your ADRs, you should be okay. That's when this lady started going on about how she's staying at the resort, hadn't made ADRs, but was told to get there at opening and they'd seat her. Well, it was like 9:15 in the morning -- huge line, way after opening. She asked a good number of us if we were staying at the Poly, to which we all shook our heads no (us and the strangers all around us), but we had ADRs.
That's when she flipped out and went to the podium. She was yelling and pointing fingers about how all of "them" aren't even staying here, but they get to eat here (referring to DH, me and the several groups in front of and behind us). She was red, shaking -- truly freaking out. I felt so bad for her family!
Somebody with some authority came out and talked to her away from the big line. They were still talking to her after we'd checked in and were waiting for our buzzer to go off. Our breakfast took a little over an hour (we waited a little for Mickey to come to our table), and as we were walking out, the lady and her family were being seated. And she was still so visibly upset, red, shaking, sweating.
So, yes, I plan, even tho I go to WDW on very short notice, stay off site so that I can eat off property easily, and it does irk me to see customers using these tactics to get a table. On the other hand, the vacationer in me who has gone to other vacation destinations agrees that you should be able to eat at your hotel if everywhere else is full. But I don't have an answer. Leaving tables open is going to tick people off. But people are ticked off now with the current system, too.