White woman here. When I do work in my yard, I will not be stopped by police. My black friends will (and have). I don't have to worry about my future son getting shot by police because he was buying candy. I don't have to sit my kids down and give them "the talk". I have never been hassled by police, I've only been followed in a store once (as a goth teen lolol), I don't get weird looks in certain shops, and I don't have people asking to touch my hair. I grew up in a white neighborhood not cut off from emergency services, nor actual family planning facilities. My parents were given loans not available to many POC. My family has had drug issues, yet they have not suffered nearly as much as if they were black. In fact, I probably have family members that would have died had they been black. There is a sympathy for white drug users, from police and society, that black people absolutely do not get. Further, I am given more job opportunities based on my race. There is more than likely a time in my life that I was given a job over a more-qualified POC because I am white and pretty. I also am helped more in school. People will tend to think I'm smarter or more serious about school than my black counterparts, and thus I get more attention and time with a teacher.
Being a woman, I am held back by a lot in society, and there is a serious mental toll that comes with that. It fucking sucks. So aside from the very tangible effects I listed above, there is the giant emotional weight that all black people have to shoulder. When people come in here with "not I! This is not me!" they are only helping themselves. They are not helping the PoC they claim to care about. It's all about them and how their feelings are hurt. Meanwhile, PoC are oppressed and killed, but they have to play nice for people to pretend to care? They've "played nice" for generations. Nothing happens until you confront the privileges of race, including your own. When you "play nice", people are more than happy to pretend that problems no longer exist. It took Donald Trump for many people to finally accept of fraction of how racist and bigoted this country really is.
PS: Actual racists love to "Not I" as well. By repeating that line and putting yourself first you, as a white person, are giving the racists an out and a cover.