Interesting post, although your post actually allayed my concerns rather then exacerbate them. From the post or comments it doesn't seem that you tried to quantify the number of lives saved by the protest. Obviously this is hard to do prospectively but it seems no harder than estimating the increased spread. For instance, if one outcome of these protests are that the http://useofforceproject.org/ policies are adopted then that might lead to 72% fewer deaths at the hands of police. Last year approximately 1000 people were killed in the US by police, meaning that after approximately 100 years the gains in your worst case scenario would be eroded. There could be many other outcomes, for instance lowering cycles of incarceration that cause much anguish aside from death. Of course this is all hypothetical but that is what we are dealing in here.

Also, a minor point is that the age of the protestors skews young, potentially meaning that the same death rate for the population cannot be applied.