rice or ricer is not a racist term. It refers to a particular direction or philosophy in car modding/culture. Nothing more. I think you're reading too much into the term...
"Rice burner is a pejorative used initially to describe Asian-made — specifically Japanese-made — motorcycles and automobiles. Many variations have also been used, such as rice rocket for Japanese sport bikes.
More contemporary use of the term rice burner, along with the prefix rice, has taken on an alternate pejorative meaning for an automobile that has been modified to give impression of high performance, but does not necessarily have any high-performance capabilities. This practice is in contrast to the "stealth" or "sleeper" style of automotive modification, where a vehicle may have major performance modifications, but the appearance remains similar to that of a stock model. In this manner, the appellation can apply to any vehicle regardless of country of origin. The most commonly modified cars are sport compacts, but the term can apply to any class of vehicle, including trucks."