All such statements invalidate the child as a person and tell them that they're feelings/wishes/desires don't matter to you. How much they sting largely depends upon the context in which they are used. Emotional disregard over little things like injuries and the like will sting the child and make them upset, but they'll usually get over it. (Of course, if such things happen repeatedly, it begins to translate into the message than mommy doesn't care about what I feel and may produce a lasting negative impact.) Emotional disregard over something much more personal, such as discounting a child's frustration that her father no-showed for visitation again, can leave a more indelible mark.
Emotional disregard can also be much more severe and blatant. For instance, one girl reports that "I started self-harm when I was 11," (a common coping mechanism among disturbed youth, which generally involves cutting themselves with a razor blade). She adds, "I told my mom, and she said, 'Why don't you just kill yourself?'" (Glock, 2009, p. 102) Taking such a dismissive attitude towards a child's serious problems or emotions is a potent rejection of the child. Such a statement shows complete disregard for the child as a person, and in these 6 little words can cause more hurt than most traditional forms of abuse. The child learned just how valuable she is: utterly worthless, and this coming from the lips of the most important person in her life. Of course, considering this girl was already cutting herself and contemplating suicide at age 11, it's very likely this wasn't the first verbal/emotional abuse her mother had dished out. It's also testament to how destructive such statements can be.