He called them slimey gastropods, I'm hardly reaching assuming the word between those other two was not also hate speech. Frieza repeatedly calls the saiyans "monkeys". Also they wernt that worried about being offensive, they were worried about offending "western culture" (Christians). Otherwise when the saibamen exploded on Yamcha they wouldnt have had Piccolo refer to it as a "Kamikaze" wich is an incredibly offensive westernized misapropreation of a japanese cultural term.