@Mutian,
Hello, Rich. I can't give you any ideas universally accepted as right for what I think is an obvious reason: not everyone agrees! But the question is "Do we need a universal morality?", not "Does everyone agree on a universal standard of morality". The standard of value should be consistent for everyone: does this further your rational, long-term self-interest (the experience of happiness in life). If something doesn't further your rational, long-term self-interest it should
not be of value to you.
If your son and you want to pursue your rational, long-term self-interest to experience happiness in your life, you must uphold the virtue of rationality, which can be defined as a commitment to thinking and valuing according to reason.
(Incidentally, it's vicious and ugly for anyone to demand a universal consensus on something in order for it to be right or wrong. To suggest that every moron must agree to something is ridiculous. I'll be calling a spade a spade until the day I day regardless of what the moral-relativists say)