When it comes to matters of opinion or personal beliefs, it is absolutely the duty of the news media to report both sides (and any extra sides there may be, on those rare odd occasions when there are somehow more than two). It doesn't matter which one they agree with, they need to acknowledge the fact that some people think gay marriage is a right and others think the gays are forming a unicorn army that will kill us all.
When it comes to matters of fact, however, they absolutely do not have that duty. Particularly when it comes to technical or scientific matters where it takes somebody with training to speak knowledgably on the subject.
If we're talking about if, say, vaccines cause autism, we need to hear from scientists. That's a scientific issue. We do not need to hear from Jenny McCarthy or Jim fucking Carrey, in the name of giving "both sides." Jim and Jenny don't get a side. They have no background in the subject, and it's one that requires fucking background.
Sure, they can talk about poisonous vaccines to Oprah or whoever is sitting next to them at the Lakers game all they want. They have freedom of speech. That freedom does not guarantee them a seat on a panel of experts.