I don't mind being offensive myself, nor do I mind offensiveness in others. It takes a degree of skill, however, to ensure that you offend the intended target.
My views on giving and taking offense are very tightly bound by considerations of the intended and actual targets of the offense. I generally do not approve of offending ineluctable characteristics: Being gay, being black, being a woman: all of these are not only inappropriate targets for offense, but also stupid: One gives offense to try to change that which offends; ineluctable characteristics are by definition unchangable.
I disapprove of giving offense when the offense is patently false. Calling liberals treasonous is inappropriately offensive, not because it's a negative characterization, but because it is patently false. If, on the other hand, you want to call liberals "fuzzy-headed", I'll probably bite the bullet and take it, since it's true often enough to be apt.
A good case study is my recent spat with Simon. I don't call Simon an asshole just because he's offensive, I call him an asshole because he makes a attack on my personal character--and Timmo's character. He aims, I think, to put down atheism and postmodernism, but he missed. Not only did he miss his (presumably) intended target, but his offensiveness is also egregiously inaccurate and entirely unsupported.
Had he made the exact same philosophical points in a respectful, non-snotty manner, even though I definitely consider his position to be mistaken, I would have engaged him on the merits. Likewise, had he (somehow) managed to offend only my philosophical positions, I also would have engaged him on the merits, albeit perhaps more stridently. Since he did neither, I simply dismiss him as an asshole.
If you try to give offense, make sure you at least hit the right target. Hit it, and I'll probably engage you on the merits. Miss it, and I'll just call you an asshole. On the other hand, if you take care to be non-offensive, then even if you're unskilled, ignorant or just plain stupid, I'll probably engage you respectfully--so long as you consider a straightforward rebuttal of your logic and sensibility to be respectful. It's your call.