I think polarizing opinions thrown at each other causes a tit-for-tat action-reaction loop. Palestine/Israel, Trump/anti-Trump, Hiroshima/Kansai okonomiyaki, etc.
Especially in this time where responding is almost effortless - all one needs is an electronic device that is able to communicate, minimal time and an urge to not let go - the cost of tossing verbal mud pies at each other is so low.