At the speed of 120 kmph, there is no way a driver can avoid an animal which suddenly comes on the road. It is not possible even if your speed is 80kmph. At such speeds if the animal is small like a dog or a cat etc. then it is better to hit it then to swerve or make any sudden lane changes in order to avoid loosing control of the car which can end up in a roll over like this. You will damage your cars front end but at least you will be safe. But if it is a bigger animal like a full grown cow or a camel than it should be avoided at any cost since larger animals especially camels when hit their body actually hits the windscreen or roof of the vehicle and can cause serious injuries to the occupants.
But yes you are right that slower you are, the safer you are. But then you have to be at around 40kmph or less to avoid such collisions.
In my opinion this is the responsibility of Motorway Police and NHA to make these highways safe for the posted speed limits. There are fences along the entire motorway for this very reason which are neither being properly maintained nor prevented from deliberate damage by the local people. Unfortunately Motorway Police is busy in issuing challans most of the times.