“Romney certainly gets a lot of grief for being a Mormon, so if he’s the RINO you’re talking about, you’re wrong.”
Please point me to some MSM articles that go after Romney based on his ‘religion’.
Just today you have this controversy about NY Times columnist Charles Blow tweeting about "magic underwear." It's not in the paper, but it does reflect how they think.
During the 2008 campaign The New Republic featured articles critical of Romney and Mormonism in politics. Newsweek's brought up the whole "baptism of the dead" thing, and you'll hear more about it from them if Romney gets the nomination.
Right now the media doesn't have to attack Romney or Mormons. If they just repeat what other people say about them, it has the same effect. But you'll see them take the gloves off if Romney is the nominee.
And of course, the mainstream media is only part of today's media landscape. Maybe not the most important part. So you have to take all sources into account.