First, any tax that’s a fixed percentage will be a higher percentage of a person’s income even that income is lower.
Secondly, there’s a point in “wealth generation” where you don’t spend everything you make. Money that you save isn’t taxed by a sales tax – so, again, the less money you make, the more it impacts you.
Regarding “earmarks” it really depends on what it’s for. As a blanket statement, “Earmarks Are Bad” is just a small government taking point – which itself can be understood as an anti-poor dog whistle, since conservatives call support for society’s most vulnerable “wasteful spending” – but you can often hear “earmarks” in reference to defense spending, which is typically a Democrat talking point.
I think that “earmarks” is actually a really interesting word, since, in a practical sense, it never means anything – or, more accurately, it always means nothing specific but I’m a vaguely specific way. The word doesn’t refer to a specific spend, but it refers to a specific kind of spend – so it sounds much more specific than it actually is.
If a politician refers to a specific earmark, they run the risk of alienating whoever benefits from it; by being exceptionally vague, they can associate their brand with fiscal responsibility without actually doing anything fiscally responsible.