I recently stumbled across some unlikely part of the web - I think it was Google reviews for a hotel in Nigeria - and people used it as some random web chat. It was very uplifting to see complete strangers just politely saying hello to each other, all from a place where good connectivity still might not be taken for granted.
It reminded me very much of how I first experienced the net in 1995: I was too amazed at talking to some random person from across the world to bother with petty arguments about politics or religion.
Now, novelty has worn off and, perhaps more importantly, for some people it's never been new - they weren't around to consciously and with great curiosity try it out for the first time. Add to this the factor of prevalence, the scale that brings and how centralized things have become.
I used to hang out on different special interest forums and IRC channels and I have to say there was as much drama, cliques, in-fighting and groupthink there as it is now. It was just smaller and more self-contained.
With today's massive community tools like Instagram, Facebook and Twitter, where there are no clear boundaries between factions or groups of interest, it's just a free-for-all: there's always someone willing to argue about something, and they're all on the same platform, which they have access to all the time, as opposed to having to deal with the diplomacy of dial-up and a shared family phone line.
If tech is to blame, it is only because it's too cheap and ubiquitous: The Great Invention that was supposed to bring us together finally has, and it turns out that we just fucking love to argue.