Don't let it get to you, it simply isn't worth it. There will always be people like that no matter how much you try to explain the content and purpose of your server. Admittedly, though, I've hosted my (99%-of-the-time unstructured) server on and off for somewhere over two years and still haven't entirely gotten used to it.
Well, since I have a variety special interest, the problem is rarely that they don't find an add-on they like, but rather that they like it too much and have to treat the entire server like a test track / firing range.