A good way to avoid confrontation is to give the student a fair warning. Explain first exactly what they are doing wrong, and what they should be doing instead. This gives them no reason to come back at you because you cannot argue with the truth. You have clearly explained to them what is wrong with their behaviour and what is expected of them. This will make it impossible for them to defend their behaviour. Also, the other students in the class will see that you are being fair. Students who are being fairly treated find it very difficult to argue with your instructions because they know that the rest of the class will view them as being in the wrong and that’s the last thing that they want.