I agree with you completely about the value of challenging ourselves with contrary views.
I'm really glad of my good friends hold polar opposite views to me on politics, social policy the way the world is going etc. Even I find it difficult to fathom how they get to their conclusions, they keep me from getting lazy in my ideas.
I'd suggest that facebook groups are not the best place to go, though. Often (not always) the content of social media groups is made up of people sharing opinions about information about facts that have circulated through large media corporations. You are as likely to find confusion and falsehood as clarity and truth.
A more fruitful thing to do is to track down the source. When the tv tells us "experts say..." it's usually easy enough to find out who the experts are, uncover source of the media report and then check that against what's been reported. An advantage of this is that you fairly quickly find out who reports news reliably, and who skews information to some agenda.
I sometimes hear my Christian friends -- even preachers -- say things such as "there's no concept of forgiveness in Islam". A very quick google search (forgivemess qu'ran) can check what the Qur'an actually says.
The Holy Spirit is perfectly reliable, but in humility I have to say that my ability to discern the Holy Spirit's prompting is deeply imperfect. Sometimes I hear the voice of God with clarity, at other times I've got it horribly wrong. Depending on revelation from God is also not an easy way to address differing views. If one person says "God told me 'A'" and another says "God told me 'not A'", its very difficult to discuss without getting into a personal conversation about who truly hearing from the Holy Spirit.