At this age, your child is not aware of the good and bad affects of watching TV. He can throw tantrums if the TV is switched off.
TV can be entertaining and educational. Channels like Discovery Channel and National Geographic offer programs that impart knowledge and values to your child influencing his personality. On the other side, watching too much TV eats into his time for healthy activities like playing with friends, eating dinner together as a family, reading, interaction with parents, extracurricular activities, or homework.
To make matters worse, TV programs which depict violence, abuse, smoking etc can result in children having bad dreams and anxiety, being afraid of being alone, avoiding school and friends. Many children don't want to have food without the TV being on. Sleeping and eating habits are badly affected.
What you can do
The ideal way to ensure that your child limits his TV time will be to monitor and explain screen time rules. Also let him know the consequence of breaking the rules. For example, if he watches TV while eating, the channel will be locked. Be firm and clear while explaining this to your child. Keep the TV in the common area of your house, not in his bedroom. During school days, he has limited free time. So setting TV time rules becomes even more important. Fill your child’s day with activities, both academic and extracurricular, which will ultimately leave him with less time to watch TV.