I really don't care if people think it's a sport or not, but in any event, motor racing is hardly on the cutting in regards to the question: "is it a sport?" That would be reserved for things like video gaming, chess, and spelling bees.
If people believe that chess is not a sport, is speed chess a sport? If speed chess is a sport (where standard chess is not), at what minimum speed must it be played at to be considered sport?
At a certain point it devolves to an argument not unlike trying to segment music into categories. What is heavy metal? Is it a sound, or a spirit? I can find Aphex Twin songs that sound way heavier than some Iron Maiden songs. Maiden generally being considered quintessentially metal. Aphex Twin, certainly not. So maybe to a certain extent it does come down to the spirit of it, and perhaps we sometimes take issue because that realm truly means something to us. We take ownership and invest ourselves, so questioning our realm as we know it, or muddying the waters with foreign additions grinds our gears, so to speak.
It's kind of stupid for it to matter as a technicality, but kind of beautiful for it to matter in the sense of what us frail humans cling to. We think we're getting upset because someone has an idiotic opinion, but we're really getting upset because it hurts our sense of self, and belonging.