So Frieza’s in kinda a weird spot where he’s both racists towards Saiya-jins, but also fetishizes them, leading to his answer here. Obviously Luffy isn’t a Saiya-jin, and the only reason Frieza said the line being referenced in the question is to make a joke about his name being the same as the slur Frieza uses for Saiya-jins, but his reasoning probably wouldn’t be much different. I kinda doubt Frieza would view humans as any higher on the species totem pole than Saiya-jins, if anything they’d be much lower.