NFL games aren't rigged, don't entertain that idea or bother debating on it. It's a ridiculous notion. Why risk a billion dollar industry to make a few more dollars by helping one team win over the other? That's nonsense.
The more realistic reasoning for bad penalties is that refs are human and gonna make mistakes. Every season, more and more rules are tacked onto the game, which makes it even more difficult to be a ref. On every play, how many responsibilities does one ref have? How many different things does he have to look for? Being an NFL ref is extremely difficult to be 100% accurate.
A better question is if you believe the NFL is rigged, then why even bother watching it? If the NFL is rigged, why bother making statements that this franchise will never win a SB unless ownership makes changes? (this obviously isn't directed at you)