"I think Toyota has a point. If I see another "its"/"it's" misuse, I will scream."
Then you need to relax. I have nearly a decade of post-graduate work under my belt and I just made the its/it's mistake earlier today. I know the difference. It's a mistake. People make them.
And, no, that does not make the mistaken person illiterate.
And they're not "mistakes" because they are everywhere and constant.
Have you tried to hire someone lately to fill in data on a database? I have. The level of literacy is appalling.