The great thing about the Hulk (and here I refer to the retarded "bah, why puny humans not leave Hulk alone" version) is that he was not only the most powerful creature on earth, but was also completely guileless. He smashed, he crushed, he singlehandedly sustained the construction trade in the southwestern United States for decades, and you couldn't really get too upset because, hey, Hulk just wanted to be left alone. No matter how many times he came around to wreck up the place, you really just had to roll your eyes and sigh and bust out the Swiffer, because, well, he couldn't help it. You were dealing with the World's Strongest Special Needs Child.
And, of course, this gave him carte blanche to mock people's appearance openly and still come across as sympathetic. No matter how often he called people Rock Face, Green Hair or Metal Head, they just chuckled indulgently. I mean, if I called my co-workers Walrus Face or Girl Hands, I'd get fired in five seconds flat, and probably punched as well. But the Hulk could get away with it, because he didn't know any better.
Also because he could turn you into free-floating bone powder with a flick of his wrist.