Hi
A professional debt collector disregards any negative (mouthy) comments and focuses on the issue at hand. The first rule of thumb is to assist the debtor in bringing their account current. If the debtor feels the need to "vent" I never take it personally... After all, they are not angry with me, they are angry for the position they are in.
If the debtor has a valid dispute regarding the debt, I work with them to resolve the issue. Once the issue is resolved the debtor is generally more willing to discuss the account with me.