What is Paradox of tolerance in Philosophy?

This is a paradoxical situation where a society that shows unlimited tolerance towards people with intolerant ideas eventually loses its capacity to be tolerant as the intolerant group destroys their rights. This was elaborated by Austrian philosopher Karl Popper in The Open Society and Its Enemies . Popper argued that for a liberal society to sustain itself, it must be intolerant towards intolerance. However, Popper did not propose that intolerant ideas need to be suppressed. It is only intolerant actions like violence that he thought need to be stopped in a liberal society.