This is fine, but it's not basing claims about what is good or bad on just your personal opinion or feeling. It's basing it on a general principle that is supposed to apply equally to everybody. That is indeed the only way of escaping the merry go round of shifting personal opinions and feelings. But it is also not perfect: not all ethical and moral issues can be resolved this way, because now you have the problem of which general principles should be used. Not everybody agrees with the golden rule, just as not everybody agrees that lynching is bad.

Sure it is not infallible but that is why I hedged the statement a little bit by saying "usually sufficient".