Kevin Williamson notes the coercive nature of the left:

The Left's last big idea was Communism. When Lenin turned out to be the god who failed, the Left undertook wide exploration for another grand unifying idea: environmentalism, multiculturalism, economic inequality, atheism, feminism, etc. What it ended up with was an enemies' list.

That and a taste for brute force.

The enthusiasm for coercion and the substitution of enemies for ideas - Christians, white men, Israel, "the 1 percent," the Koch brothers, take your pick - together form the basis for understanding the Left's current convulsions. The call to imprison people with unapproved ideas about global warming, the Senate Democrats' vote to repeal the First Amendment, the Ferguson-inspired riots, the picayune political correctness and thought-policing that annoys Jonathan Chait, the IRS's persecution of conservative political groups, Barack Obama's White House enemies' list, the casual violence against conservatives on college campuses and the Left's instinctive defense of that violence - these are not separate phenomena but part of a single phenomenon.