Why have liberals become so intolerant? They think nothing of denying someone as prominent as former Secretary of State Condoleezza Rice from speaking on a college campus. They embrace activists who shut down speakers. They publicly shame people for the slightest deviation from liberal orthodoxy.
For them everything from science to the law is “settled” once they get into power. Progress is a one way street. Their mindset is the very definition of closed-mindedness.
The easy answer would be “they are all bad people.” But frankly that’s a cop out. Not all liberals are bad people, any more than all conservatives are angels. No doubt among the fevered minions of liberal activists there are people with, shall we say, psychological issues, but that doesn’t explain why so many otherwise reasonable people are so beholden to liberalism as an ideology.
The short answer is that it pays. A lot of people in and out of government benefit. Liberalism also makes people feel good. Whether you are politician dispensing government benefits or the citizen receiving them, liberalism hides the self-interest and sometimes even greed that motivate people.