Because, as it has been shown throughout the entire history f this country, when people who identify as white get scared of something their decision is to kill it!!! That has always been their excuse for committing any atrocity against any group they targeted.

"I was afraid for my life."

This attitude we have about anger exists among Black people not because stereotypes are bad, but because we have learned the hard way that showing anger gets us nothing but a quick, and usually quite nasty, death.