It's certainly more morally complex than just scamming somebody. Money is property. People generally agree that once you earn your money, it belongs to you. Is the government automatically entitled to part of it? The Boston Tea Party, the Women's Tax Resistance League, and Gandhi's Salt March are a few examples where people said no.
Usually in this context the "evaders" will refer to it as tax resistance or tax protest. It is a form of civil disobedience. The government being disobeyed, of course, is unlikely to see it that way, and in a modern context, would call it evasion. https://en.m.wikipedia.org/wiki/Tax_resistance
The Indian example is especially poignant because refusing to pay salt taxes was one of their key strategies for achieving independence from the British, and they managed to do it without firing a shot. So yeah I'd say refusing to pay the salt tax was a big win morally and probably saved a lot of lives.
What the best examples typically have in common is that the government in question didn't possess the consent of the governed. In the case of the British WTRL the refrain was "No vote, no tax." If the government won't let women vote then what right does it have to tax them? Women weren't able to indicate consent (or lack thereof) via the political process, and they were ultimately successful in their argument that this taxation without representation was unjust. Incidentally this line of thinking was expanded upon decades later across the pond in the US, which ultimately decided via the 26th amendment that it was immoral to draft men into the army when they were still too young to vote, and lowered the voting age to 18.
See also https://en.wikipedia.org/wiki/List_of_historical_acts_of_tax... for hundreds of examples you might or might not agree with ...!