How long are canned goods and jarred sauces still good after the best by dates?

I really need help with this. I am taking care of my father and I have discovered most of the pantry foods in his house are far past the expiration or best by dates. He is insisting they are still good, but I think they need tossed. So far when I notice something really old, I go to the store and buy a new one and toss the old when when he is not up. The other day he pulled out a jar of oyster sauce that had a date of 2007 on it. I refused to use it when I cooked out steaks. The next day I bought a brand new one and he noticed it wasnt the same jar he pulled out for me. He was really angry at me for wasting it. Am I being foolish throwing away old food?