You can't be a liberal and a Muslim. There is no liberal tradition in Islam. You can be a pro-choice, pro-gay, pro-feminism Episcopalian or Buddhist or Reform Jew. If you hold those views and also consider yourself a Muslim, then you're being unfaithful to one or the other. I think there's plenty of ideological room for a liberal sect of Islam; but we're still waiting for someone to create it.
I personally know a number of liberal Muslims. But I'll let them know that according to a guy on the internet they have to choose one or the other now.
I'll double-check with my gay, Green-voting Muslim friend shall I?
On topic - there's a nugget of truth in what Maher is saying. The teachings and texts of Islam are very problematic. That is not to say there aren't significant issues in the Bible... but most except the the most extreme have contextualised and rightly dismissed the worst of it. Which is what the vast majority of Muslims in the west do.
The issue I have with Maher on this isn't that he's racist, because I don't believe he is, it's that he fundamentally doesn't understand. He makes the primary mistake that all people who criticise Islam make - primarily they don't understand that it's as diverse and fragmented as Christianity. One of guests, whose name escapes me, was a Palestinian who argued with him that he didn't understand how Islam is structured or how it works. All Maher could say was "yes, I do... here's what the Quran says you do" etc etc. Would he know about the impact of the rise of the Wahadi in Saudi Arabia after WWI and what that did to Islamic thought and culture in the Middle East? Or the difference between the sects of Islam and what they teach, how the study their religious texts... of course not, because then he can't rant from his high-horse.
Personally, I don't have time for any organised religion, and yes, Islam does pose issues... but to not know or care about the fundamental nuances and diversity of ideas and views, history and not even acknowledging the role played by Islamic thinkers over the centuries in science, architecture, navigation and philosophy.
If you don't acknowledge a difference between Modern Islam in a secular society and Fundamentalist Islamism... then you're an idiot and in Maher's case, deliberately so.
