Because the "opposing view" did not gun down 5 police officers and BLM never called for killing men and women in uniform. 

I'm guessing that you may not agree with their mission statement http://blacklivesmatter.com/guiding-principles/ but it is clear that it is the opposite of violent. 

There is no moral equivalence between BLM and the white supremacist racists. The former seeks to bring up others so that all have equal and just treatment, while the latter fears that result and seeks assure their own supremacy at the expense of all others.