the reason why i can't really agree or disagree with whether it's racist or not is because context matters, especially over the internet. if you are being very matter-of-fact with physical similarities (height, weight, facial hair, outstanding features, etc.) in claiming the two look similar, then it's not racist. but if the only reason you're saying he looks like CJ is because of race and nothing more, then yes, most people would find that racist.
just a sidenote: there is debate around whether people can be racist toward white people or offensive toward straight people since they've been #1 in society for a long time (at least in america), but i'm not educated enough to speak on that specifically so i won't