Here's why:
* It's a generalization: People of Japanese descent, like any other population group, have a wide range of facial features. Eye shape is just one feature and varies greatly.
* It's based on a misconception: The epicanthic fold, the fold of skin that sometimes appears on the inner corner of the eye, is a common trait in many East Asian populations, including Japanese people. It's a genetic adaptation, possibly related to protection from harsh sunlight and cold climates, not a sign of "slant."
* It's offensive: Using terms like "slanted eyes" perpetuates harmful stereotypes and contributes to discrimination.
Instead of focusing on physical features, it's important to recognize the diversity within any population group and treat all individuals with respect.