If you boo Prince Harry are you racist against Brits? I mean they are just a symbol of the country! If you don't like them just be quiet. Or not.
The world isn't black and white. Some people might boo due to racism, some for the specific BLM message, some because they don't want political messaging. That's why it's a bad idea to try to force a politically divided audience to espouse a divisive political view.
No one had any issues with previous racism campaigns. Why do you think this has had such a negative response?
Booing a political gesture doesn't make you a racist by default. If you actually believe that I'll be very disappointed.