But morality tends to become so ingrained into us that we are often unaware of it.
For examples, what's your reaction to the thought of child molestation? having sex with your children? walking nude downtown? [these are obviously rhetorical questions]
Sorry to butt in but...
I've for as long as I can remember have questioned my feelings. Why the hell am I feeling sad or guilt. Often I couldn't find a real reason for it. So many things influence why we feel what we feel. Some of it I'm aware of some not.
I always felt I was wasting my time feeling angry or sad. There's lots of fun things I could be doing but I'm stuck here feeling angry or sad and I can't even precisely identify why. What a waste.
I got so pissed off about being controlled by my feelings, I decided I wasn't going to be controlled by them anymore.
As far as your questions, generally society decides what behavior is acceptable and what is not. In most cases, going against society is too much of a hassle. I'm usually happy to adapt to whatever those norms happen to be.