Morality is not a subjective matter. I think that morality is an objective thing, and that people think it is subjective because it is "always changing." I don't think that is true. I think that morality itself is a constant thing, but we think it is changing because our perception of morality changes. Morality itself does not change.
Morality is constantly evolving and advancing with our society.
We can point to history to show us when we thought something was right, and as we grew more intelligent, learned it was wrong.
We can point to science when we learn that pack animals share morality similar to ours, and the more intelligent they are, the closer their morality is to ours.
There is, however, no evidence of objective morality, or any way to test it.
Nor is there any testable, logical source of a "universal" morality of any kind.
Morality, understood as a code of conduct differentiating intentions, actions, decisions and things into good/right and bad/wrong categories, cannot be objective, as no intentions, actions and decisions have intrinsic characteristics of being good/right or bad/wrong, or have intrinsic value. Such actions etc. are always valued subjectively, no matter how, and then objectified through social discourse.