To say “I don’t believe in rights,” is like saying, “I don’t believe in language.”

Uttering the phrase contradicts your claim. Humans created language in order to constructively communicate. Language is real because people agree on the meaning of words.

In the same vein, humans created the concept of rights to facilitate peaceful human interaction. Rights are real because people agree (sometimes without realizing it) on what constitutes a right.

Even as someone utters, “rights don’t exist,” they are exercising their most basic human rights.

It is self-evident that they believe they have a right to live because they are alive. They believe they have the right to liberty; aren’t they saying what they wish to say? And haven’t they taken the time to ponder their beliefs? They have done so in their best attempt to understand the world, and thus apply that understanding to the pursuit of their own happiness.