Why don't progressives want to talk about how Islam has been hijacked?

In America, other contemporary ideologies are routinely and openly debated in classrooms, newspapers, on talk shows and in living rooms. But Americans make an exception for Islamism. Criticism of the religion—even in abstraction—is conflated with bigotry toward Muslims. There is no public discourse, much less an ideological response, to Islamism, in academia or on Capitol Hill. This trend is creating an intellectual vacuum, where poisonous ideas are allowed to propagate unchecked.
My own experience as a Muslim in New York bears this out. Socially progressive, self-proclaimed liberals, who would denounce even the slightest injustice committed against women or minorities in America, are appalled when I express a similar criticism about my own community.

Compare the collective response after each harrowing high-school shooting in America. Intellectuals and public figures look for the root cause of the violence and ask: Why? Yet when I ask why after every terrorist attack, the disapproval I get from my non-Muslim peers is visceral: The majority of Muslims are not violent, they insist, the jihadists are a minority who don’t represent Islam, and I am fear-mongering by even wondering aloud.