In a case like this, the only person who can fix it is the CEO. First document the behavior with dates times and person who said something offensive. Them when you have a good long list, have your manager bring it to the CEO. Personally I would concentrate on this part because it is the most likely to get action and is the least subjective (and totally unprofessional for an HR, it is a firing offense):

The HR team constantly talks about employees behind their backs in very derogatory language, including loudly offering up details of employee complaints/issues which should be strictly private.

Having a lawyer write a cease and desist letter to the CEO if no action is taken could also help this. Sometimes a public shaming in the press works (but does put your job at risk, so don't do it lightly or without expecting the worst consequences.)

If you don't want to pursue this legally, then the best bet is to move on.

In a case like this, the only person who can fix it is the CEO. First document the behavior with dates, times, and the name of the person who said something offensive. Then when you have a good long list, have your manager bring it to the CEO. Personally I would concentrate on this part because it is the most likely to get action and is the least subjective (and totally unprofessional for an HR, it is a firing offense):

The HR team constantly talks about employees behind their backs in very derogatory language, including loudly offering up details of employee complaints/issues which should be strictly private.

Having a lawyer write a cease and desist letter to the CEO if no action is taken could also help this. Sometimes a public shaming in the press works (but does put your job at risk, so don't do it lightly or without expecting the worst consequences.)

If you don't want to pursue this legally, then the best bet is to move on.