I imagine that plenty of people 'report' people after disagreeing with them politically.

Zuckerburg has political ambitions, a little help from the Facebook moderation team might earn him a few favors. He certainly wants that infrastructure in place once he runs.

Easier to sell ads if users don't have to deal with differing opinions. Arguments are hard to avoid and disrupt the casual consumption experience.

Conservative voters probably represent a much smaller portion of facebook's user base than liberal voters, given facebook's age demographics.

There is definitely an assymetry in what kind of hard-line political pages are likely to get banned. They have relaxed a bit in the last few months, but many political pages constantly have to worry about "getting zucced".