*Ultimately* these things always get down to fine points of definition. Technically, if you understand that culture is the primary determinant of human behaviour, and think there are very few differences between people that are due to race/genetics, you are probably aren't racist. But a lot of people define racism more broadly, to include having subconscious prejudices, to drawing attention to race unnecessarily, and so on. On broader definitions, either almost everyone or everyone is racist.

Personally, I think defining racist too broadly isn't particularly useful, so I wuldn't say 'we are all racist', but I would say we can all behave in a racist way unless we try very hard not too. If you think you aren't racist, that probably means you are only racist occasionally, probably without even realising it.