Since I agree with @GulliverFoyle on this subject, I’ll give an answer too.
The problem with equating #allspeciesmatter with #blacklivesmatter is the same as equating #alllivesmatter with #blacklivesmatter.
The problem isn’t an undervaluing of other species…it’s choosing to override the specific egregious inequality faced by African Americans in the U.S. by lumping it in with everyone else.