It is self-refuting since it says one's moral beliefs are based on the culture they were raised in. Well then; one could argue that someone who believes that morals are relative is based on their cultural upbringing.
Since relative table manners are self refuting, there must be objective table manners.
I have a hard time with the idea of objective morals mainly because it necessitates a black and white approach. Every action is Good, Evil (capital letters) or not morally relevant. For example, blowing your nose cannot really be considered a moral or immoral action. So it is not morally relevant.
There are moral dilemmas we have all heard that we struggle with understanding whether the actions in the given context are Good or Evil (capital letters). If objective morals exist, then there is a correct answer for every one of those situations. We may think Good or Evil or whatever. We may debate it. But how do we know who is right? Where is the answer key? I've yet to find it. In the end, we are left with our own judgment, which as far as I can tell, is based entirely on culture and personal experiences.
So, tell me, Gill, where can I find the answers?