this has to be the biggest thing in politics and economics which winds me up at the moment
tax avoidance = legal (and pretty much everyone does it in some form within the law)
tax evasion = illegal
Winds me up too, maybe they should be renamed to avoid people confusing them so much, we can call avoidance "careful spending" and evasion "stealing", much easier for people to get their head round

Why does it wind you up so much? People will always want to find loopholes that allow them to pay less tax.
I read it as him being wound up by people and the media confusing the terminology so much, not people doing it.