You may have not expressed offense but you responded with a defensive denial (“Not me.”) rather than address any of the other stuff in the OP. I saw no request for clarification from you, only protest. And unfortunately this appears to be a classic reaction whenever someone talks about race on this board.
I agree with the idea that “everyone is a little racist on the inside”. That everyone includes me, by the way. There are so many forces in our society that train us to group each other by race before all other traits, and its human nature to form certain beliefs about people based upon their particular group memberships. When those two things interact together on a societal level, odds are racism will be a signficant byproduct. Combine this interaction with the existence of certain racial disparities (like poverty) that only serve to reinforce stereotypes about a particular group (“black people are disproportionately poor because they are lazy and shiftless”; "blacks are disproportionately in jail because they’re bad people), then you should expect to see even more racism in the population. Some people will be more affected by it than others, but it would take a special person to be 100% immune from it all.
So, yeah, everyone probably has some racism inside of them. It’s not something to get bent out of shape about, but being aware of it can help it from causing problems.