Unfortunately, most people find quite difficult to ignore such insults. Our brains are wired to go to the negative; it takes a lot of work to change that. If someone is already struggling with any number of issues, these kinds of insults can be devastating. This is why it's hard to get out of a cycle of negative thinking, which affects emotions.
Changing this is possible; it's just that it takes conscious effort and often support from a professional and/or or family/friends.