The problem I've run into is definitions. How one person defines murder or child abuse is not the same as someone elses definition. There are no universal absolutes and this makes defining anything as always immoral tricky.
You've already answered your own question to an extent. Depending on the source that one uses, there will always be several definitions of what is and what is not morally correct. For instance, someone who believes that the bible is the absolute authority on morality would define homosexulality as being wrong. An athiest who does not believe in the bible, or God for that matter, feels that if society allows it and the law of the land allows it then it can be morally acceptable. Another example could be capital punishment. Some bible followers feel that a person who murdered another human in cold blood should be executed because the bible says to give an "eye for an eye." While other bible followers feel that his life should not be taken and to let God sort it out in due time(isn't this the position of JW's these days??). So even here, people who profess to follow the bible can have differing opinions on right and wrong.
In the end, it is all about definitions. But definitions can be taken from a great deal of sources. We have the Bible, dictionaries, *pseudo* intellectuals, lawmakers, think tanks, etc., and the list can go on and on. Typically though, someone's definition of right and wrong stems from their own life experiences and what they want to be right and wrong.
If you're looking for that universal absolute, you will have to wait until (God) appears and tells the world in person that such and such is unequivocally right or wrong and your idea of right and wrong is f**ked up. By then we will all be dead, so this issue will not matter to anyone of us anymore.
