Good vs Bad

I always thought i knew good from bad and have brought my children up understanding my understanding of that difference.  Today i read that someones good may be someone else's bad : confusing ? tell me about it !!!

For example - some believe that to smack a child as a last resort is a good thing, to teach discipline and respect.  For others it is bad and takes away that child's humanity and free spirit.
What are our intentions behind our judgements of what is good or bad though?  In the above example the intentions on either side is good, however to vote for the former by someone with a violent anger issue would not be so good.

"Most of us, most of the time, tend to act with intent, trying to bring about some desired end.  But nature doesn't act with intent.  A Buddha doesn't either.  Acting without intent means acting out of wholeness - out of seeing the whole."

I rarely examine the reasons behind my knowledge of good vs bad.  Maybe i should.  Some things that i see as good may well be bad for someone in a different culture or living with different conditions.