Spelling out the difference: evasion and avoidance.

I am getting quite angry with the hosts of letterwriters in the media proclaiming their leftie 'soak the rich' immaturities.
Many state that 'tax avoidance must be stopped'.
Apparently this will save quadrillions of pounds and obviate the need for any harsh measures whatsoever as the government attempts to clear up Labour's unholy mess.
Perhaps these people should be asked if they want to pay taxes that do not apply to them!
Tax avoidance means just that! You pay what you are obliged to and do not pay what you do not have to!
Tax evasion however, is illegal. It means not paying taxes which you are obliged to pay.
Are these writers so stupid in parading their ignorance of the difference between the two cases? Or is it that they do recognise the difference and are utterly barking?
In either case - the left does not emerge with a great deal of credit for their intelligence levels!