I’ve found an interesting article regarding “difficult clients”. The author told the story better than I could (into a more delicate way)
I will use here some of his quotes and let you enjoy the whole article in his website.

No matter which field we belong to, our most common complaint is “My client is really difficult to handle.”  And yes, being a graphic designer, I think we are the ones who mainly get to deal with the most complicated clients

And things I’ve heard a few times from my clients too:

“I have a neighbor that has a nephew that does websites too… So, I’ll go to him, I can bet he’s cheaper” (yes, everyone’s a designer nowadays)
“Our CEO likes them (boxes) right angled. Make them rounded. And why this color? Make them red…” (both CEO and Marketing person were women)

Anyway, go read this article. And for a complete experience over “the client is always right” read this one: “Ode to the amateur logo”