I think the argument would be (and I'm not sure how they could prove such a thing) that they were not omitting facts, but actively suppressing facts and allowing the spread of (what ended up to be) misinformation. I'm not a lawyer, of course, and playing Monday morning QB of sorts.

EDIT: Though, I think this only applies to news sources, which they've been ruled to be not as. Though that ruling may be overturned if they actively suppress certain information.