Why do Leftists have trouble understanding that ISLAM is not a race?

They protect radicals from criticism by calling critics of intolerance "intolerant". They ignore that the critics are pointing out the intolerance of radical Islam and the easy comparisons between radical Islam, terrorism and fascism. (Arab racism, anti-Zionism, anti-Christian rhetoric, terrorism, suppression of moderate Muslims, suppression of Baha'is, genocide against black Christians and animists, denial of Berber rights, persecution of Christian Phoenician Lebanese, lack of respect for women, gays, etc.) All of these ideas are intolerant but the Left calls critics of these ideas intolerant while protecting the rights of the intolerant. This makes them co-conspirators, or at least, enablers to this movement in Europe, Africa, the Middle East and other parts of the world.