Why? It's not like luggage/items are damaged mid-flight due to turbulence - they are damaged by careless airline employees.
They may warn you, but why does that give the airline the right to be so careless?
This is why....
The airline will definitely not take responsibility, because if you read your contract of carriage (the fine print that comes with your ticket) it explicitly states that they are not responsible for damage to electronics in checked baggage, including gate-checked baggage.
He should have known that the airline isn't responsible for damage to electronic things placed in checked luggage, and yet was still too lazy to just reach into his bag and take out his laptop before handing over his bag.
So yes, I think it's his fault. Regardless of how careful they are when handling your stuff, his bag may end up at the bottom of a pile of suitcases and other bags.