It's because he's not trying to humiliate the government. He's just trying to give something back to his community. He's an intelligent young man who hasn't forgotten how little he came from and wants to help others. The simplicity of it, the HUMANITY of it, is exactly why he's humiliating Johnson and co because they simply cannot conceive of this. They've come from plenty and have been taught to aim for plenty more. Essentially, they're found themselves bewildered by - and unable to respond to - basic kindness, humility and a desire to make things better for people other than one's self. The Tories cannot understand why he isn't just pulling the ladder up behind him in the way that, as an example, Priti Patel is by creating immigration criteria that her own parents would have failed.
It should not have been difficult for a government to respond to Rashford as an individual. That he had to build a network via social media to feed children has created something much, much wider. Which is why The Fail have to try and comfort their readers by holding him to an impossible standard because they cannot possibly engage with the reality without challenging their entire politic.