I feel like there are two questions inside this one question.
The first is about showing your cards. I think that most of the time, the benefit of showing your cards and tilting an opponent is outweighed by the harm of giving all of your opponents information (there's usually more than two of you at the table). I think there may be times when you can manipulate your table image in beneficial ways by showing, but those sorts of attempts can also be transparent to any thoughtful player. So for the most part, I don't show my cards, bluff or not. I think there's more benefit in withholding information.
I think the second question is about the ethics of intentionally tilting another player, and this is a little more complicated. I think a person can absolutely go too far. Guys like Martin Kabrhel or Tony G are just bad humans IMO. I think there are things that are required of us as humans before what is required of us as poker players, and not being a total jerk in order to gain some possible edge fits that role. On the other hand, within the game structure, you can act in ways that wouldn't be cool in normal life. In normal life, I tend to try to be honest and transparent most of the time, and try not to intentionally mislead people solely in order to benefit myself. That's because life isn't a zero-sum game, and poker is. In poker, I'm almost always trying to either mislead people, or encourage them to make bad decisions, or both. Given that, I will happily try to tilt other players with my play, but avoid trying to tilt them in ways that have nothing to do with the play at the table.