Is very difficult to avoid buying from Amazon if they offer you the best price for whatever you are wishing to buy.
Why pay £1000 outside, when they price the exact same thing at £500 (for example). By seeking to save, I am doing what the company also does - both legal under current laws.
They may not have been upfront with all their taxes, but I doubt they dodge VAT and deduct taxes on their employees wages. As someone else has already pointed out their Board has a legal responsibility to their shareholders to minimise costs etc.