Ive noticed a universal truth when it comes to things I dislike about jobs:

Rudeness: be it customer, employer or co-worker...nothing is more irritating than a mean, nasty, rude person. Its just a downer...and its hard not to resort to rudeness as a comeback

Asking for my opinion and then dismissing it as if I'm some sort of moron. If you had a solution in mind, why did you ask for my opinion?