Notice how people are always quick to be suspicious of Chinese food but we don't see the same treatment of all the various "normal" products people regularly consume that contain red dye 3 (like pez, strawberry milk, etc.).

ETA (Edited to Add): see Chinese Restaurant Syndrome, for example:

The controversy about MSG is tied to racial stereotypes against East Asian societies.[25][26][27][28][29] Herein, specifically East Asian cuisine was targeted, whereas the widespread usage of MSG in Western processed food does not generate the same stigma.[30] These kind of perceptions, such as the rhetoric of the so-called Chinese restaurant syndrome, have been attributed to xenophobic or racist biases.[31][32][33][34][35][36]

Food historian Ian Mosby wrote that fear of MSG in Chinese food is part of the United States' long history of viewing the "exotic" cuisine of Asia as dangerous and dirty.