I think the biggest lesson to learn is 1. knowing that people judge you based on what you say in your videos and 2. the demand of deals. With the first point, your viewers judge what you say. You may think it's a funny joke, but, if that joke is offensive, there are some that take it literally. I'm one of the people who take racist and sexist jokes pretty seriously. That doesn't mean you should censor them out, it is just something you need to keep in mind. Pewdiepie (I dont think) meant everything he said, but, because he said it, he can't prove that and it made him lose deals.
Also, being the face of businesses is hard because you represent them and what you say affects their business. It's a whole different aspect of YouTube and that's why you need to know what you're doing before you enter into these deals.
There is a video that explains these points in better detail that I watched today. I can link it if you want to watch it. I agree with you though. It does suck.