The oldest virtue, and the glue that holds together our social fabric, is civility; therefore in order to survive as a nation, we've got to start treating people with respect--ergo we've got to get a lot more serious about the tawdry breaches of civility.
Here's my suggestion on how to make things a little better for everyone: If you find an insult typed on your receipt, let the manager know about it and ask how the issue will be resolved. If he or she smirks or shrugs, let other customers and friends know--this is where Facebook and Twitter comes in handy.
If I found out that an establishment turned a blind eye to the mistreatment of customers, I would not support the establishment until the whole problem was resolved, which sometimes means dismissing offending wait-staff and managers.
While we're at it, if you know someone being uncivil online--un-friend them, letting them know why you are doing so.