First, I must say that I am amazed at the idea that a parent would be "angry" with a child KNOWN to have a problem with wetting...since it would obviously be no surprise to said parents, there is hardly a reason to be angry at anyone under the circumstances-except, perhaps, themselves.
That being said, any answer to the question would depend entirely upon how one approached the child or teen in question, and how one respected that person and their condition.
If they've been previously subjected to all of this "anger", then I would have to say that the situation should be handled with sensitivity, to say the least.
There are, of course, other alternatives, and other protective underwear, besides diapers, to be considered. Regardless of how anyone who isn't subject to the condition feels, the dignity of the child in question would be the FIRST consideration in the matter, as far as I'm concerned.
In any event, I am quite sure the child would appreciate any assistance rendered in a caring, discreet, and private manner.