I think just about anything would be better than what he said.
I wouldn't say that it was a different time, or anything about the circles I kept.
I'd go with:
Clearly, I was ignorant of the harm my costume could cause. In the seventeen years since that photo, I've learned a lot about Canada's history of racism and how harmful stereotypes further marginalized racialized Canadians. If I had better understood the iniquity that racialized Canadians faced, and continue to face, I never would have engaged in what I now recognize and denounce as a gross and harmful caricature.
My detractors imply that people can't change. They're wrong. People can change, and our town can change. I work hard to make this a thriving, welcoming community and I know that we shouldn't let anyone distract us from the important work we have to do.
Can't use 100's in a lot of places.