It's difficult to do so, because it's hard to say what can benefit a person who is wealthy already.
I mean I can point to data that suggests that people who earn better wages, get headstart, have libraries in their community, get a college education, etc are less likely to commit crimes, but your wealth probably means that you can afford good security.
I can say that in a more egalitarian society, vaccinations would be free, and thus you are your children are less likely to get diseases, but you have good health care, and so this isn't a huge issue.
So I guess the best way is to point out that in a more egalitarian society with free or low cost education and funding for research, general progress in the sciences would happen faster. You get better medicine, better technology, can potentially live longer. Also such an economy will grow more quickly, and while if there were more stringent taxes you may not gain as much of the pie as you could, a bigger pie would cancel that out.