I actually only use the word "rattlecan" to provoke language Nazis. True it's stupid sounding, but it is descriptive unlike "spray paint" which could describe any paint delivery system that sprays. Professional painters usually use the term "paint-gun" as the generic term to describe air powered paint application devices, and I favor the term "spray-can" to describe an aerosol based disposable paint application device. Air brushes also spray paint, as do robots in auto plants, house painters also use paint sprayers, but I wouldn't recommend using one of those on your bike.
So yah, don't use the term Rattlecan if you don't like it, but if you're going to demand others stop using it to satisfy tour own sense of propriety, at least come up with a better alternative than "spray paint". That's like saying "I think Cup 'o soup is dorky, just say soup", or "I think PB&J sounds silly, why not just call it a sandwich"