呵呵, i believe that 's 男人最不是东西了！ro 男人没有一个好东西 but actually the one who says this herself is usually a "bad girl"

笑死了 for example : a pretty girl screaming to the poor guy who chasing her: 想追我？你是个什么东——西！ I've also heard: 男人, 还能算是东西嘛? or something similar. As for the justification, only when you are want to start an argument, or have already started one and want to make it worse.

nothing, just some stuff like"who do you think you are" sure it will cause fighting.

Sounds like "Who do you think you are" in English. In this way, people can express their anger and hatred when they want to fight.东西means stuff. People are definitely not stuff.

Because it is rude. It means "What are you?" not "Who are you?" You don't call people 東西. A humorous way to say it could be "甚麼南北!?".