All Lives Matter does not undermine the BLM movement; instead, it is a better term to help fight for equality for black people and other minorities. Black people are not the only minorities to face racism and inequality.
Every minority group in America is facing some struggle and oppression. Incidents with racists misidentifying a Sikh person as a Muslim or the chanting of “Jews will not replace us” are examples of these racists not being able to differentiate between minorities. Singling out one particular group would not solve anything and will only alienate people. It would also hinder progression in the overall fight against
Chanting "Black Lives Matter" (BLM) moves the focus from the overall issue of racism and narrows it down to one victim group. The slogan "All Lives Matter” (ALM) can serve as an umbrella term to combat this problem. Adopting the phrase will eliminate the implication that black people are the only ones who are affected by it.
Previous activists such as Martin Luther King Jr. advocated for equal rights for everyone and promoted nonviolent tactics and strategies. They welcomed everyone and fought against all injustice. BLM is attempting to do that and is undermining its message and purpose. Using an umbrella slogan like ALM would also dispel any doubt about the BLM cause and message as it promotes the message of shared humanity.