The problem with high taxes and complex tax laws is that inevitably those who are wealthiest are best able to use the loopholes built into the tax code to avoid paying taxes. Even if you support sticking it to the rich with higher taxes, chances are they aren't really paying it. If tax increases include increases for the middle class then they are hurt far worse even if those increases are minor.
You can see what kind of pernicious effects that had on the inequality situation in the United States in the 1950s. The rich had all the money and they hid it from the tax man. Meanwhile, in doing so, they weren't deploying their capital in ways that were productive for jobs and economic growth. They were hiding it in all these little ways that Congress permitted them to hide it.
Source: Why the Rich Actually Love High Taxes - Foundation for Economic Education