I want to be fair here. Not all liberals defend Islam. In fact, most that I know do NOT (except in the sense that they defend the rights of all humanity). But for those who do, their defense of Islam is inexplicable, considering their traditional political positions. Let's go over a few "liberal" positions for analysis, shall we?
The environment: Liberals are quick to condemn our dependence on fossil fuels in the west. They are quick to decry our environmental atrocities, while failing to hold Islamic countries accountable for the same.
Equal rights: Women are second class citizens in Islamic countries, and homosexuality is justification for murder in many villages, without consequence from the national government.
Free Speech: Do I even have to go here?
Freedom of Religion: There is but one God, Allah, and Mohammed is his messenger.
Democracy: virtually nonexistent
Civil Liberties: The Hussein regime in Iraq was a horribly ruthless and oppressive regime. Islamic countries are constantly at the top of Amnesty International's watch lists.
Fair labor standards: Again, Islamic countries come in on the low end.
Now, I will again reiterate that not all liberals defend Islam. But for those who do, I would be interested in knowing precisely WHY you do. The United States is far from perfect, but we have made TREMENDOUS strides in ensuring liberty and opportunity for all of our citizens, while working to preserve and better our environment. Why do you not hold Islam to the same standard?