Not sure about parent commenter, but it's not that uncommon in ethical theories. A good example is Act Utilitarianism, which holds that the moral value of an act is solely based on its consequences, specifically its increase on net happiness (how to quantify that, of course, is the big problem).
Thus, a scenario could be developed, however unlikely, in which any particular action would be moral or immoral if the world was defined so that it would increase or decrease net happiness. For example, suppose we knew with certainty that one of three individuals halfway around the world was about to initiate a nuclear launch, but we had no reasonable way to find out which in the next few seconds. AU would clearly support launching a drone strike against all three--against the human right of due process--we would make two families sad, but certainly prevent millions of people around the world from being very sad.
Human rights are a fundamentally deontologist concept (as opposed to Utilitarianism, which is a consequentialist theory), basing the morality of an action on its compliance with certain standards and not on its consequences. For example, you might argue that someone has an inherent/inalienable right to do X, even though it would cause great harm or make many people unhappy. For example, you might argue someone had the right to publish classified information that would almost certainly lead to the start of a war.
Also, you say that human rights are a human inventions--some philosophers would argue that they are inherent (either from god(s), by virtue of reason, or some other external source). This is the position the US Bill of Rights and Declaration of Independence take, informed by the Enlightenment tradition. They claim that certain rights are not granted by the government or society but intrinsically exist and thus must not be infringed (taking a Deist position, they cite a generic "Creator" as their source). A consequentialist could support a lesser, human-sourced set of rights that made a general rule, but not an inviolable one.
The concept of human rights says that every human who is born is entitled to this list of rights. I think that's silly for many reasons. Most important is that that list of rights is completely skewed to a Western, liberal view of the world. It's basically imperialism.
I mean you can't be saying you don't believe they exist, because they're a human invention. Are you saying you don't believe they should exist?