Yeah, those examples are discussed in the ZCommunications article, as effective in only some situations. ("True as this is, don’t forget that these movements were addressing state and societal brutality against entire groups of people as the primary focus of their strategy; state violence was thus an illustration of their point. In the case of a holistic movement primarily focused on elite rule instead of state repression, police violence is a distraction. It may earn you sympathies, but it does not help to make your point in any clearly illustrative manner, as it did in these examples.")