Hardly a shocker here. The media has accepted the belief that opposing gay marriage is now officially a fringe position. So their coverage is going to reflect that belief system. My theory is this; as the entertainment media normalized gay marriage public attitudes shifted. This shift was dramatic in the last five years.
Sensing this shift the news media gave up any pretense of objectivity(well, they still thought they were fooling people) on the issue and went all in. Groups like Pew usually argue that bias is difficult to measure; that part of this is very interesting.