Hello Daniela,
I do find what the waitress said to be offensive and stereotypical. I am troubled though for the same reasons by how you describe the African American mindset as one in which “crime and prison is an adult rite” and unacceptable to decent humans of any skin color.” I am actually unsure how this part of your post came through the moderation.
The Coffee Room has at least one poster who is African American, per his story of coming to Orthodoxy from a Christian background. As offensive as your remark was to me as a Caucasian, I can not even imagine how offensive it would be to an African American person.
Negative stereotypes based on ethnicity are not acceptable or tolerable, in the CR or out in the world, no matter which group is the subject of the stereotype.