I’m not familiar with Popper’s work, but I see that quote (“tolerate everything but intolerance”) used to rationalize intolerance toward perfectly tolerant individuals. Any evidence that the target is “intolerant” suffices, no matter how tenuous or contrived (“an intolerant person once said a good thing about <target> therefore <target> is intolerant). This seems similar to the concern you expressed about the GP’s philosophy. Did Popper lay out more stringent criteria for what constitutes “tolerance” and “intolerance”?