Blah blah blah Ian can do no wrong, blah blah picking on kids makes me feel good about myself, blah blah.
With all due respect Dan, and while I can see the basis for your argument, I have to disagree somewhat with the point to which you have taken it.
Ian is human and is thus capable of mistakes. He's also got a good reputation though and those mistakes seem to be pretty few and far between. Mostly taken care of in a manner that seems pretty reasonable and fair when they were brought to his attention.
Reputation does matter, some skepticism of claims of wrongdoing when the person being accused has a good reputation is normal and even beneficial. If the overwhelming majority of experiences dealing with someone (in this case Ian) are positive and fair, then that pattern of behavior is highly likely to continue. Not guaranteed... but it's probable that his position was in line with his previous history of customer interaction and quality.
As to picking on a kid... Some of it crossed some lines (cracks about his appearance, calling his girlfriend fat). Some of it was more a criticism of the manner and method that Ralphie chose to behave.
Shows are often an environment where it's difficult to sit down and have a conversation- there are noises, there are distractions, there are other customers or potential customers, there are the necessary attentions which have to be paid to the animals on the table. An adult, behaving as an adult, would look at the environment they found themselves in and have some patience if they were trying to find some resolution of a problem. The conversation might be broken into segments as Ian dealt with his other, more immediate responsibilities, it may have had to wait for a lull or for someone to cover Ian's tables. Discussions about resolution and restitution are also ongoing, evolving processes until one side or the other drops an ultimatum, a final offer, a last word. Staring contests, swearing and yelling and storming off, shouting accusations and eventually resorting to a mouthpiece... none of these are reasonable, adult behaviors.
At nineteen, I don't think there's any excuse for behaving like a petulant child. Ralphie's own descriptions of his actions and words at the show, the descriptions and perspectives of others being even worse, paint the picture of a person who's emotionally and socially retarded. Dealing with that kind of juvenile personality, as that personality throws a temper tantrum in the middle of a public place... I can't blame Ian at all for writing Ralphie off as more trouble than he's worth.