Because they're fundamentally about maximizing personal gain regardless of the cost to society. This is in direct violation of the covenant upon which societies are founded. Most people take this violation as an immoral act.

Are you implying that public officials and the public sector is not trying to maximize their personal gain (regardless of the cost to society)?

Which covenant is the founding of societies based upon?

Please enlighten us.

Most people in my country deem high taxes immoral.

By 'society' here, I take it that you mean the interests of large, highly taxed countries?

Shame and phrases like “violation of the covenant upon which societies are founded” are tools used by people to try to convince you to do things that are in their best interest.