People like to compare racism (along with other forms of opression) to abuse. For example, if a parent told their child they were too stupid to go to college, and the child consistently received this message along with other negative opinions on their worth across their whole life, then you could call that verbal abuse.

The US as a country used to say blacks were too stupid for higher education, and measures were taken to keep them out of universities. Think of segragation too.

Getting your feelings hurt after a single misunderstanding or a deliverate take down might not be likely to cause trauma, but if you consistently received negative opinions on your worth, intelligence, etc. across your whole life, then that might eventually, slowly break a person.

The idea is that microagressions add up.

It bothers me so much when people say that children are fragile flowers and one misunderstanding could traumatize them, it's misleading. When children are traumatized due to abuse, it's because abuse is actually a lot nastier than a simple misunderstanding or a parent's low mood one day. But racism and other forms of opression are nasty too.