Do you ever use the phrase "long time no see"? It is treated as innocuous today but it is rooted in a mocking jest at broken English spoken by Chinese immigrants. The funny part is that I know Asian Americans who say it without knowing where it came from. You can be misinformed about something that is fundamentally racist.

The twisted MSG belief system is just a less overtly racist version of "Chinese restaurants serve cat and dog". i.e. This ethnic food is not trustworthy and worthy of derision, as are the people by extension.