Actually, in that list of sticky links posted the other day, there was one excellent entry in the myths section. The myth, *BSD is better than (insert other system)
This is user opinion only.
Some people will put a GUI on a server.
When you call someone foolish, you've gone a long way towards closing their mind.
If they're inexperienced, give your reasons why you don't think it's best practice, and let it go. They can choose to listen to you or not. If you think they're foolish, well, you stated your opinion. If you come in saying, Only an idiot would put a GUI on a server, then, especially when you DON'T know what Ubuntu-desktop is, (nor do I--for all we know, it's a minimalistic GUI for certain possibly appropriate uses--probably not, but the important point here is that you're saying, "I don't know what it is, but it must be wrong."
It's possible, for example, that it's a home server for family files, that will double as a desktop and they need some sort of awkward hybrid. Just for example.
Judging from your posts here, however, I'm sure that you are giving intelligent, diplomatic arguments. Without looking at the thread, if I say, "You're doing it wrong," I'm doing exactly what I say not to do with the Ubuntu desktop thingie.