Some of the people who say everyone is racist are actually just acknowledging that humanity's rather fucked up history in regards to race has had many far reaching effects that persist even to this day, and one of those effects is that there are many fucked up beliefs/attitudes towards certain racial groups that are pervasive enough that everyone has probably fallen for some of them either consciously or subconsciously.
Or at the very least, everyone is at rather significant risk of falling into at least some of those fucked up beliefs/attitudes.