This is inaccurate and dangerous too. The man armed to the teeth who killed 5 Texas police officers was a sympathizer to the BLM. The guy just a month ago armed to the teeth at the GOP baseball game who, if not for good fortune, would have killed many high ranking U.S politicians. THAT'S scary.
The violence from the left has become worse, and the rhetoric/language has become more violent, and worse normalized, from the late night comedy shows to celebrities and even left wing politicians. Worse, the same consequences that someone would face for threatening Obama does not exist when they threaten a Republican president.
I've seen this movie before. There was an intense and constant effort on everyone to paint right wingers as dangerous with little attention paid to anyone else, there are some trying this today by having people lose their livelihood if they have conservative beliefs. In 2001, even though Israel warned the West about Islamic terror, nobody listened and we all know what attack occurred that year. The West was so ill equipped that the CIA and FBI had very few Arabic speaking agents and had to go on a hiring spree to find them as there was clearly a new threat. I suppose like in Europe today, it was inconvenient to the narrative to believe that some foreign immigrants who don't share American values just might pose a threat.
I don't know that you can call radical Islamic terrorists left wing supporters, but most certainly they share some of the same anti-American, anti-liberty views that many on the alt-left share. From toppling statues to punishing you mercilessly for differing opinions. If I were a betting man I would suggest very few are card carrying Republicans.