Also, I'm no Trump supporter, but attacking him based on his appearance isn't unlike him making fun of a disabled person
It's completely different. You need a sense of humor.
Trump wasn't joking, he was mocking a disabled reporter in front of a crowd of supporters. His intention wasn't to make others laugh, it was to hurt the reporter's reputation and mock his disability.
Chup's intention was to make others laugh, it's called a joke.
The reason it's funny is that Trump, who has attacked the appearance of pretty much every one of his political opponents, their spouses, media personalities, celebrities, former beauty queens and pretty much anyone who has criticized him, put out a press release threatening repercussions if the media continued to use 'unflattering' pictures of him. It's double funny because he attacks Liberals, calling them 'special little snowflakes' because they want 'safe spaces' while simultaneously asking for special treatment from the media because he doesn't want to look fat in photos.
It's ironic when someone who constantly attacks other people's appearance, whines about others 'attacking his appearance', especially when he's literally calling people fat pigs and whining about someone using an image of him with a double chin. Irony is generally pretty hilarious.
If you don't get the joke, that's cool. If you don't understand it, that's cool too. Drawing a false equivalence between mocking a disabled person in front of thousands of supporters and intentionally posting an unflattering picture of someone (which, to be honest, isn't even that unflattering considering that he's a 70 year old man) who constantly ridicules other's appearances is just ridiculous.