“Heretics were often most bitterly persecuted for their least deviation from accepted belief. It was precisely their obstinacy about trifles that irritated the righteous to madness. Why can they not yield on so trifling a matter?”

A generalization that has a lot of events to back it up. For example: in the Unified Socialists of Amerika (USA) the occupying statist theocracy infesting the land bitterly persecutes the least deviation from accepted beliefs and the canons derived therefrom. In office, or otherwise employed, zealots of the here referenced USA exhibit extreme irritation at non acceptance to their righteous madness.

Muslims consider everyone else as heretics and they don't mind killing them. When will we wake up to the dangers of Islam.

When there are obviously insane zealots who will kill anyone that insults their God/prophet/savior, we can more easily assume our own correctness and ignore our own hypocrisy. Those that broadcast their tolerance are often loud and long-winded in their attempt to veil their own obvious intolerance.