Talking face to face with someone allows you to see they're human. Most conflicts in history come from a lack of "cross cutting cleavages" (titter titter [double pun]) in society, IE lack of interaction between people of various beliefs and social status. You're more likely to tell someone to shut the fuck up if they're bashing gay people if you have a gay friend or family member. Most often the most isolationist and reactionary groups are the most homogeneous and segregated populations (if this sounds a lot like many well, christian or religious communities, then you may have stumbled upon why there religion is an issue that often deteriorates into the dehumanization of others).
The term "cross cutting cleavages", by the way, comes from various political scientists describing modernization theory, and why urbanizing societies tend to become more tolerant, liberalizing societies (namely because cities bring a lot of very different people into very close contact with each other). Look up Daniel Lerner or Seymour Martin Lipsit if you want to read more (or for my favorite account, read Ashutosh Varshney, although his specific analysis is in India and he uses the term "building bridges", which is basically the same thing).
The internet however, does not really bring people together in the same way as face to face interactions, hence many individuals take the offence and often instigate inflammatory and extremist debates, only to be fed more by individuals like myself who are in it for the lulz.