I see no reason to allow "membership" in both, as the tenets are typically diametrically opposed to one another. You can't believe in both at the same time. It's like trying to say, "I'm a Christian atheist" - doesn't make sense.
It is worth noting that, the way "liberal" and "conservative" or defined on this site, or more accurately, left
undefined, a person can be conservative and liberal at the same time. Both words have several definitions, and, while I can't speak for this side of the fence, at WWMC, we have no desire to pick apart those definitions and figure out which types of liberals we represent.
Given that, there is no reason why somebody who believes in the innerancy of the Bible
must also oppose gun control and abortion and support limitations on the central government. A person who supports gay marriage might also vote Republican for economic reasons and believe in the inerrancy of the Bible (and, for reasons personal to them, see no contradiction between that and the other two views.)
So, yes, a person
can be liberal and conservative at the same time. Which reframes this question a bit. CC was founded specifically because non-fundamentalist and moderate conservatives felt out of place in the Fundamentalist forums. If I recall the conversation, it was pointed out that WWMC welcomes people who are not wholly liberal, but the fundamentalist forum isn't all that accepting of moderates, and so people who were simply "conservative," but not to the degree of fundamentalism, had no place to hang their hat.
What was the point of creating this place if one of the first actions is to close membership to those who might also want to discuss their liberal side? In short, to exclude the moderates? The very people CC was created for?
This might be none of my business, as I have no intention of claiming membership here, but it does effect members of WWMC.
And, being a moderate once, I do remember what it was like to never fit in anywhere.