Indeed - "slaves" got changed to "robot slaves", while "narcotics" became "rare species" and "liquor/wines" became "beverages". You can still trade firearms, though, so its not entirely squeaky clean...

Nintendo would have had a hell of a time censoring firearms from videogames. Nudity, slavery, narcotics, and alcohol are easy; violence and firearms form the basis of many/most popular video games.

Probotector is Contra @50Hz with all humans replaced by robots, but still lots of firearms and violence.

I never understood why UK and Europe got probotector instead of contra, maybe it was due to Germany's very strict game censorship?

Yeah, that's my guess. Violence towards humans in video games was often prohibited in Germany, so drop it for the whole region, because two releases is hard.