No ones life is in danger from keyboard mullah's, and you shouldn't let threats from these keyboard Mullah's scare you into shutting up. I've been posting on this board for almost 12 years and gotten into many, many heated debates with our conservative brethren. Heck, sometimes just my name ends up triggering some of them.
Look at many of the other staff members and their views, many liberal as well - if, as some allege, this board has the 'backing of the Pakistan Army', what does the presence of so many 'patriotic liberals' (distinct from the extreme liberals like Bukhari, Haqqani etc) suggest to you?
If you're concerned, keep your online identity anonymous. The staff here is never going to reveal anything personal about you (not that we know anything beyond your IP anyway).