That image is a ridiculous simplification and using it to get to an effective tax rate is idiotic. If Sunak earnt money only through income tax then his effective tax rate would far exceed that of the nurses. Investments and dividends are taxed differently to income tax so of course the effective tax rate will be lower. That isn't because he is an evil man but rather because that's how investments and dividends are taxed, the same rules apply to everybody.
We all live and work in a system where we pay the least possible tax that we can legally. If you have an ISA then you are saving and gaining in a product designed to avoid tax. Based upon the above should ISA's be banned on the basis of morality then?
If you want to increase the rate of taxation on assets such as shares then I hope you are prepared to pay for the implications on yourself because where do you think your pension is invested? Are you happy to take a drop in your pension value and gains so that somebody like Rishi Sunak will pay more tax?
We live in a time where every single demographic is taxed more than ever before, and the taxman takes in more than ever before. The problem is not how much tax is collected but rather where the hell does it all go?
It's not an idiotic simplification, it illustrates extremely well how the rich pay proportionately less tax because unearned income is taxed at a higher rate than earned income. We used to have a progressive tax sytem where the rich paid proportionately more and I think this is what the poster is getting at, not that what he is doing is illegal.
You also seem to be assuming that everyone will sympathise with your argument because it might impact their private pension or ISA's, whereas many many people (nurses included) can't afford a private pension of any real worth and have to rely on the state or occupational pension and don't have ISA's stuffed full of shares to worry about.
I am interested in why you say that value of pensions would drop if unearned income was taxed at the same rate as earned income. In the UK Pensions holding are mostly held by Corporations who pay tax at Corporate tax rates so I don't understand why the value of Pensions would fall. I am happy to be educated but don't see the connection when we are comparing the effect of the tax on a very wealthy individual and a normal person.