In my opinion?
What were the relevant actions?
David found Bathsheba attractive -- presumably (I will assume that their affair was mutually consensual), Bathsheba was attracted to David. Nothing wrong with that.
David and Bathsheba carried on an adulterous affair. Was that wrong? It's hard to say. Considering that Bathsheba was probably little more than property to Uriah, and the whole honor thing might have made things a bit dicey (look how David had to kill off Uriah to hide the affair), a secret affair was probably the only way at that time they could have acted on their mutual attraction.
But then, when Bathsheba became pregnant and their affair was about to be discovered, instead of admitting to it, taking the consequences, and using his power to protect Bathsheba, he decides to kill off Uriah. That is pretty much wrong.
This is just my opinion, being raised in 20th century North America.
An interesting note: in the punishment for this sin, God allows David to choose to have a large number of his innocent subjects die in a plague. Pretty wrong there, too, so it appears that the author of the Ten Commandments doesn't exactly have the moral high ground either.
Never believe anything in politics until it has been officially denied. -- Otto von Bismarck