My experience in marching for causes began as a boy in the '60s marching to end segregation. Since then, I marched to protest war in Vietnam, Iraq, and Afghanistan. I marched for gay rights. I marched to oppose Arizona SB 1070, which racially profiled Hispanic Americans. I suspect I made other marches that I'm not remembering now—for most of my life, I've believed in putting my feet where my mouth was. While we individually were sometimes accused of being anti-police, no one described what we were doing as "anti-police marches."
But describing #BLM as "anti-police" is understandable, especially after their "Pigs in a blanket, fry 'em like bacon" chant:
The general public simply doesn't know what #BLM intends: Is Equal Justice the Goal of Black Lives Matter? - Rasmussen Reports™ The full report is behind a paywall, but bits are quoted in an article that tries to spin #BLM's confused message in terms that its leaders believe: New Rasmussen Poll: Majority of People Say #BlackLivesMatter Movement Doesn't Matter, as White Denial Over Racism Continues:
The poll also found that 51 percent of Black voters say the Black Lives Matter movement supports reforms to ensure equal treatment under the law, and 30 percent say it doesn’t, with 19 percent unsure. On the other hand, 55 percent of white voters say the group does not support criminal justice reform, and 21 percent say it does, with 24 percent uncertain.#BLM is unquestionably effective at two things. It's promoted itself very well, and it's made many people think that an issue which affects all Americans of all races, and especially poor Americans of all races, is only an issue for black folks.
Related: A handy list of white victims of police abuse, or Why #BlackLivesMatter should be #AllLivesMatter
Black leftist critics of antiracism and BlackLivesMatter
Three boys shot because of toy guns: Tamir Rice, Andy Lopez, Nicholas King - #DemilitarizeThePolice