Not all of them. They're people with different personalities and different mindsets on things. If you fought for 3 to 4 years along side someone and then had to kill them, I'm sure it would take something out of you.
Some of you're points are quite true but the people with the different personality thing is drivel. Remember that the soldiers have all been cloned from the same man and all of their genes and DNA match his. Basically, you have an army of Jango Fetts.
DNA does not dictate personality. Twins and other multiples don't act alike and their DNA is identical.
Also they've stated in several instances that the clones all act differently. They decorate their armor and give each other nicknames based on personality, as well as going off and having relationships and families outside of the army. Some of them even defected from the GAR because they hated how they were being treated like disposable slaves . If you're not sure, check out the Clone Wars tv series (as bad as it is sometimes), and the Republic Commando books and video game. There's also several cannon comics that are just based on the clones.