Refusing to take responsibility for damage to my luggage

My bag got damaged (soaked in some unidentified liquid) while traveling on a Greyhound bus from East London to Bellville. Now Juan-Pierre at customer care insists that I must prove that they were negligent. I have sent photos showing the nature and location of the damage. Any reasonable person can see that the bag would have to have been upside down to be damaged in that manner. What "careful" person would transport their own luggage for over 1000 km in an inverted position. Maybe he has a different understanding of what constitutes negligence.

Very quick to hide behind flimsy clauses about Greyhound not providing insurance for luggage. Greyhound may as well put in simple English and state clearly that they will handle our luggage carelessly and not be liable for any resulting damage. In fact, that should be in big red letters : BE WARNED, WHEN TRAVELING WITH GREYHOUND WE MAY DAMAGE YOUR LUGGAGE AND DISMISS ANY CLAIM YOU MAY TRY TO LODGE. And then, in small print add "we are a giant, we can do as we please and there's nothing you can do about it. We have people at customer care whose job it is to squash any claims for damages".