I just watched the entire thing. I think she actually did a good thing in a very subliminal way...but it takes a while to realize it. Here me out.

She spent lot of preparation for this speech. It's not a rant. It's a very carefully planned out speech, that she drafted and rehearsed. Although the title is "Dear Fat People", I think she intended it to be heard by friends of fat people. This is the most important thing.

She claims she had to watch a family of obese people take advantage of their condition at the airport, which I doubt happened, but uses it as a rally cry to remind everyone that fat people exist and to feel some resentment towards a person who has wronged you in one way or another, who also happens to be fat.

But she periodically tries to say that she's not referring to people who have just a little but chub or people who have a disease. She claims to only be criticizing fat people who are proud about it, who pass it on to their children. I think most people will agree that it's one thing for an adult to be obese, but when a parent allows their children to become obese, that's just bad parenting.

Her conclusion wraps her entire speech up, where she admits that she sounds like an asshole, but is doing this because "your friends" aren't, and she also claims that she's doing this because she's selfish and wants you be around longer. She's intentionally demonizing herself here, and no one would ever thing she has any good intentions.

So how can this "hate speech" be good? Because a lot of overweight and obese people who want to lose weight lack the will power. They need support from their friends and family. Support just like OP wrote above, and all the many commenters below. She's not telling people to shame fat people more. She's being a caricature of people who shame fat people, which I think will resonate with friends of fat people to be more conscientious about how they treat fat people. The friends learn from her that making rude jokes isn't helping. The friends see from her that it's not a topic that should be ignored, because you might end up losing your friend from heart disease or diabetes.

Or...I could be completely wrong, and this woman is just a stupid spoiled brat who wants to be famous.