Macbeth was not born evil. There is no indication that he was genetically predisposed to behave badly and there is no indication that he was historically, culturally, or personally determined to become a murderer or a tyrant. This is all true prior to the witches' prophecies in Act 1, Scene 3. So, prior to these prophecies, Macbeth is/has been a loyal subject to Duncan and, by all accounts of the previous battle, a successful soldier.
And although one could argue that the witches manipulated him, the fact is that in the end, it was Macbeth's choice to commit murder. Since he was not evil prior to these prophecies, it is clear that Macbeth had been, and still was, capable of loyalty and doing the right thing.
One might have sympathy for Macbeth because he is encouraged by his wife to be bold and ruthless, and because he is manipulated by supernatural beings (witches). But the counterpoint to that sympathy is that Macbeth eventually allows those influences to get to him. More importantly, we can see how Macbeth struggles with such decisions to commit murder. He is so conflicted that he calls upon his dagger to motivate him. Like the witches and the encouragement of his wife, Macbeth is now convincing himself and thus motivating himself, against his "better" judgment to go through with the crime. "Thee" refers to the dagger:
I see thee yet, in form as palpable
As this which I now draw
Thou marshall'st me the way that I was going. (II.i.48-50)
He agonizes over killing Duncan and he is filled with anxiety after having done so. He isn't just worried about getting caught; he has a guilty conscience. And this indicates that he knows what he did was wrong but yet he still did it.