We argue with people of color about their lived experiences of racism. We say "not all white people!" and "all lives matter" and totally miss the point. We ask people of color to educate us, and to be "nice" about it. We talk about our good intentions. We bring up the times we were also treated badly.
Why? Because we can. As white people living in white supremacy we have the power to take that focus because society values our words more than those of people of color. It's hard to even recognize we're doing it. But it has to change. We have to be able to comprehend a point about racism without demanding that a person patiently hold our hand and explain it to us very delicately as to avoid hurting our feelings.