||Does intolerance necessarily prosper in a tolerant society, or is deemed to decay? To address the question, I build an evolutionary model of competing (political and/or religious) beliefs. In the model, individuals are assumed to gain from having beliefs. The gain may increase with intolerance of the belief (premium). High intolerance, however, makes strong believers fragile in a society of tolerant people. Having examined evolutionarily stable states in two specifications, I demonstrate that (for any positive premium) heterogeneity cannot prevent intolerant beliefs from spreading out. A sufficiently small increase in intolerance, when premium exceeds losses from fragility, allows intolerance to spread. Intolerance is vulnerable only as long as the premium is non-positive. This finding can also be interpreted as follows: unless fundamentalist confessions are proved to be vital for individual human existence (positive premium), a tolerant society needs no intervention to preserve tolerance.