But how did you come to that conclusion? It seems more like a preference than an objective truth to me.
Why, of course it is a preference. It is also objective, as it must be. True subjective morality would be utterly meaningless and pointless.
But what on Earth would an objective truth be? Nothing that exists in the real world, I would think. Objective truths are things like mathematical formulas, whose very power comes from renouncing any responsibility towards the real world.
It seems to me that some reflection on the nature of moral choices is necessary at this point.
Morality is a function of rationality and behavior. It just can't exist otherwise. It is built of and limited by sentient beings' ability to perceive reality and act on it. It involves dealing with both uncertainty and the understanding of the likely results of actions and omissions.
To put it in another way, the space of existence of morality resides between uncertainty and prediction. Morality is unnecessary when there is certainty, and it is impossible when there is no ability to predict outcomes. It is the discipline of using choices in order to decide how choices must be restricted.