I've also never seen video of him inciting people. But supposedly he did? Does someone have the actual evidence?
For one, he specifically gave financial and logistical support to Wolfgang Halbig so that he could harass the families of the victims.
It's clear how these people operate. Everything is black or white, good or bad. If someone is bad, then they are wholly evil and every allegation against them is true, no proof required. The key goal is to destroy him and the exact justification used is an unimportant detail.