Conversing with strangers

So last night on Facebook, a religious discussion got started. I know, dangerous. Or at least tricky.
I posted two things. The first was in response to my friend's status update. (This is a real-life friend.) The second was to a response by one of his friends. Someone I don't know.
This is new territory for me--this conversing with strangers. I'm old enough to be cautious about what I put online. But I'm also cautious in another way; I don't know the person I posted to, which on the surface is OK.
But in another way, not.
I don't know what bothers him. I don't know what makes him tick, makes him laugh, makes him interesting. All I know is a few lines about his religious beliefs.
People laud the Internet for bringing people together. I get that; I'm addicted to Facebook. But something about bringing people together to "converse" via computer, and separated by perhaps thousands of miles, seems artificial. It's artificial because I don't know how much to divulge when I don't know the person on the other end, not to mention pretty much anyone in the world who has access to a computer.
And then there's the real downside: People who don't know each other blasting one another because it's easy. (I'm thinking primarily of comment boards). You think you're countering a position when in fact you're communicating with a real person you can't see.
How is it with you, conversing with strangers?