Suppose there’s something we care about other than happiness. That thing surely can trade off with happiness. If rights matter then some number of rights violations are as bad as some amount of suffering. This poses a problem.
Suppose we have two states of the world. In state of the world 1 every person violates every other person’s rights billions of times a second but every single person is very happy. Every moment of existence for every person contains more joy than the sum total of joy experienced in the history of the real world.
State of the world two has zero rights violations but every person is in extreme misery—experiencing more suffering per second than the sum total of all suffering experienced in world history. If there are enough rights violations, then the person who thinks rights matter would have to hold that world one is worse than world two. This is deeply implausible. A world where every second everyone experiences more misery than the sum total of all misery experienced during the holocaust and slavery cannot be worse than a world where everyone has immensely excellent lives.
A similar case can be made for virtue. A world where everyone is virtuous and miserable is worse than one where everyone is vicious and happy.
This is what happens when you give a utilitarian human rights, they abuse the concept and proclaim it refuted by using circumstances that will never occur.
You conveniently do not mention what right is being violated or how that’s occurring. You also assume that rights can be traded off with Utica directly and thus assume the torture v dust specks problem that Rights based views rightly reject.
In a world with immensely happy people that were only happy because they had been forcibly wireheaded, I would consider it to be correct to find that world non-preferable.