Kendrick Lamar is finally getting support for his decision to NOT buy his sister a baller new car -- of course, his backer is the company that made the umm ... frugal whip.

Kendrick took heat on social media for buying his younger sister a brand new Toyota Camry as a graduation present. In true "no good deed goes unpunished" fashion ... haters accused the multi-millionaire of going cheap on his kin.

But Toyota thinks K-Dot will have the last laugh.

A rep told us Toyota sees the choice as more "smart and thoughtful" than cheap, since Camry has a good track record for longevity and reliability. Plus, they're made in the U.S. -- so props for buying American! Sorta.

All good points, but Floyd Mayweather's kid would say ... so is a Benz.

We kid. Props to Kendrick, and his sis, for practicing what he preaches.