I use twitter and have a quick and snappy discussion in about a dozen exchanges, many times with known people like journalists, columnists etc. Of course, you must carefully choose who you interact with or follow. I find engaging in discussion of such topics as politics and religion to be futile, and economics is intertwined with politics. I only do it when I see something intolerably incorrect or foolish and I just have to engage with the fellow (as in this https://xkcd.com/386/).
On a cynical note (or realistic if you will), I don't think topics like politics and religion can be discussed in a civil manner. If they are, then those discussing are not getting to the meat of the matter because once you get there, you are bound to hit a nerve or two and the civility facade comes right off. Even IRL those who engage in civil debates are more careful about appearing civil than actually debating effectively. The interwebs, with its anonymity and all that, allows one to be much more freer in bringing out their ugly side right of the bat (though sometimes it could be a persona adopted for the kicks).
On a cynical note (or realistic if you will), I don't think topics like politics and religion can be discussed in a civil manner. If they are, then those discussing are not getting to the meat of the matter because once you get there, you are bound to hit a nerve or two and the civility facade comes right off. Even IRL those who engage in civil debates are more careful about appearing civil than actually debating effectively. The interwebs, with its anonymity and all that, allows one to be much more freer in bringing out their ugly side right of the bat (though sometimes it could be a persona adopted for the kicks).