Fat liberation Twitter has been amazing about The Whale. They don't even actually agree about why it's so offensive. (Well, other than Brendan Fraser isn't fat enough, so it's appropriation.) I've seen some complain that it's too negative, others that it's too positive, some that it's too unrealistic and others that it's too realistic about being fat. On and on, for millions of tweets for months.
There was a great 30 tweet thread from some chick who spent the first few tweets talking about how she paid for a different movie to sneak into The Whale and then the rest was about how horrible it is and how all fat people need to avoid it for their mental health though she of course never exactly specified why this was the case.
That "fatdoctor" guy is one of a number of claimed fat medical professionals on fat liberation Twitter who spend all day talking about how there's no scientific proof that being fat (defined by these people as being like over 300 pounds or more) is bad for you, that there's more proof that being thin is bad for you and that all of medical science is a thin plot to genocide fat people.