When the personal allowance increases, it benefits higher rate tax payers more. This is simple logic, because it is them that pay more in the first place; 40% not 20%.
5 friends go to the pub once a week. The bill always comes to £100 and they share it according to their income. The highest earner pays £40, the others pay £30, £20 and £10, and the lowest earner pays nothing.
After 4 weeks the friends are surprised and delighted when the landlord gives them £20 back for being such loyal customers. They split the £20 in the same proportion, with the lowest earner receiving nothing.
The lowest earner kicks up a fuss. "That's not fair - I'm getting nothing!" he says, and carries on "As usual its the rich exploiting the poor"