That's tough.
I do feel that it was necessary to stop the coup before it was allowed to happen, and really, waiting for the Uchiha to attack would had been irresponsible. The end result would had likely been another ninja world war and the complete destruction of Konoha, that couldn't be allowed to happen.
That said, I do feel that Itachi had alternatives that he could had taken. Itachi himself admitted that it may had been possible to stop the coup without killing anyone that he didn't try. I also feel that he could had told people about "Madara" and rallied Konoha and the Uchiha together against a common enemy instead of being played against each other as they were.
Also, Itachi was the worst double-agent in history. He did nothing to help Konoha or stop Akatsuki in 10 years. To be honest, Orochimaru helped more than Itachi ever did.
The majority are against Danzo and what he did for the Leaf and the shinobi world, so I wanted to see if Itachi gets the same treatment.
Don't you just love the hypocrisy?