So, two things:
1) Since we can agree that the stated goal of BLM vs white supremacists is very different, we should be able to agree that counter-violence statements from a group whose goal is violence should be treated with less respect than similar statements from other groups.

2) The leaders of BLM, and most of the people who consider themselves part of the movement, agree that violence against those police officers who are simply doing their jobs to the best of their ability is harmful: http://time.com/4400330/st-paul-protests-philando-castile-black-lives-matter/