I presume that none of us on here know how much money these rich celebrities give to charities and good causes, whether directly or indirectly via 'voluntary tax'. It may be that they do all CHOOSE to give away a lot of their wealth on a regular basis, and they are angry that other similarly-wealthy people don't do the same, so that the burden on poorer people could be reduced across the board. Rich people usually don't care about the 'little people'; but they may just lend half an ear to what their wealthy peers say.
Would it be better if, instead of these people coming together to say "We are wealthy - we, and everybody else who is wealthy, should be compelled to pay more tax as standard" they just shut up about it and enjoyed their privilege without caring about less well-off and poor people?
How can they win? It seems to be coming from a good place, but they're having it thrown back in their faces.