In some cases I think it is appropriate to be a dick to someone. I employ the method when someone else either lies, purposely misrepresents me or my words, involves people I care about in order to be nasty to me, or someone I know is trolling just because they can. Those types can be very annoying and quite frankly they are easy pickings when it comes to demonstrating a point. I will be a dick after I have presented my argument or asked questions and the other person decides to be disrespectful to me. I will walk away, block(online), push the keyboard away or call you a motha fucking asshole. Some people can be engaged with conversation and some cannot.
"All atheists are rational". Yeah, bull shit. No particular group, no matter how large or small has the market of rationality, skepticism or critical thinking all to themselves. If you are an atheist who dares call religious people stupid and yet you have beliefs in the "power" of astrology, homeopathy, believe all sorts of conspiracy theories, hate women and gays, deny science when it highlights the absurdity of your passionate beliefs etc, how do you think you're any better than the label you give them?
Calling people "sheep", "closed-minded", or "stupid" shows me you do not have or choose not to use better ways to demonstrate your point. If that is your "A" game, it is weak. Those words are automatic kill conversations and quite possibly can ruin any chance you have at building coalitions on shared beliefs/positions. I do not think theists are stupid but I do think they are wrong. If you insist on calling people stupid, you may burn a bridge that can never be rebuilt. No amount of apologizing can fix it. Be strong in your position but do not go out of your way to be an asshole to someone else.
Side note: Some peoples notion of "respect" is so guarded that any discussion of their beliefs(in anything) is seen as disrespect. Such a notion should not be accepted as good. I once had a Philosophy professor tell me just how shitty a paper was written when I turned it in to him. Was he remarking on my overall personality or my other beliefs, my livelihood or my upbringing? No. He was targeting one specific thing and that thing only.