What's so bad about taking a tail of pills?

My father is a walking hospital case. He has high blood pressure, diabetes, psoriasis, stress etc. I've noticed that he has to take a lot of pills, but he's got such a hectic schedule that he takes them all at a time, together. I've tried telling him that it isn't healthy and that Heath Ledger died because of it, but he won't listen to me. He says that I have to show some concrete evidence against this (he's a lawyer) and that he doesn't think that there's anything wrong with it. Please help, and thanks in advance for any advice! =D