How can you be avoiding a tax that legally you should not pay?
In this thread the discussion revolves around the legal reduction of an individuals tax liability...
Using the word avoid in the context you have done, if Muon is to be believed, an example: You can 'avoid' paying as much income tax by claiming for expenses relating to your business.
If you are talking about Tax Avoidance, as in the legal and/or literal term, then Tax Avoidance is the legal minimising of your tax liability.
Both are legitimate in the context of the law.