The Cold Civil War began in late December 2000 with the SCOTUS Bush v. Gore decision.
I think it was back during the Clinton Impeachment. That was when the partisan divide started. Each side supports their guy regardless of what they do.
Trump just made Politicians obsolete and this rage level of decorum will continue long after his Presidency is over. It is now the new norm. The demonized W. Bush too. Expect more of the same only at an “11” level