hah yeah that was what I was trying to hit at. If you say 'my bad' is wrong, then I think 'I'm good' is no better either? cos when someone asks 'how are you?', it's more like relating to your state of health or wellbeing. Whereas if you reply 'I'm good', it alludes more to your behaviour (well-behaved) or your ability (see beh zai).
as someone said, the butchering of the english language!!