Milksnakes are members of the genus Lampropeltis, which makes them kingsnakes. Period. There is absolutely no way to define a kingsnake that does not include milksnakes as well.

Look it up in any dictionary you care to:

milk snake n.:
Any of various nonvenomous king snakes of the species Lampropeltis triangulum ranging from the eastern and central United States south to Ecuador, often having red, black, and yellow or white bands.

milk snake n : nonvenomous tan and brown king snake with an arrow-shaped occipital spot; southeastern ones have red stripes like coral snakes

Furthermore, toads have been classified as frogs for quite a few years now.