What should TAs do if students disrespect them?
The TAs in question should speak with the director of the course first and foremost - it will be important to have that person "on their side", and they likely have a better idea of what actions are available to the TA.

In a more general sense, my opinion is that you try to treat those students with a sort of detached professionalism, but you are under no obligation to go the extra mile to help them. And you are absolutely within your rights to ask them to behave politely.