There is no reasonable objection to the idea that "Black lives matter".
Equal treatment is reasonable as a demand.
But if they object to the notion that white lives matter too , or that police lives matter also , they are leaving the implication open that only black lives matter to them , and that could be criticized.
If there is a demand for the right to abuse or ignore the police with impunity, that is not reasonable.
If they are being reasonable , why shouldn't anyone be reasonable right back?
When a person who asserts that police are necessary or that all human lives matter is booed , there seems an unreasonable element enters the conversation.