[He bites his lip and manages to stop himself pointing out that Spike killed him too - twice - and bit Ianto too. She's not as accustomed to such things as they are, or certainly he is, anyway. Even so, this still feels like an over-reaction, to him.]
It's nothing to do with your 21st century sensibilities! We re-souled him, Martha. He's not the same man who bit you.
[He's even more certain of this after having just talked, at length, to Spike about it.]