If you are interested in learning whether "outside agitators" intentionally turn peaceful protests violent, read the first chapter of Anarchist, Republican... Assassin". It describes how anarchists are trained to disrupt peaceful demonstrations and the techniques used to bait police into over-reacting. It provides historical information dating back to the "police riot" at the 1968 Democratic Convention and to recent riots following the murder of George Floyd in Minneapolis.
I saw it close up in D.C. in 1970 and NOLA in 71. One of the anarchists, who was tasked with trying to turn demonstrations in NOLA into riots, described their tactics to me. He told me he was traveling around the country trying to turn civil rights and antiwar protests into violent confrontations with cops. That was one of the "inspirations" for the book.