I have to take issue with your anecdote Mangara. They say never judge a person until you have walked a mile in his shoes, and if you then decide to hate him you are at least a mile away and have got his shoes too.
Neither you nor I know the ins and outs of your friend's business, and it may well be that, for example, he has made substantial pension fund contributions over the last couple of years (realising that he does not have the benefit of a gold plated teacher's index linked pension!). This would be eminently sensible, result in him significantly reducing his current tax bill and create a future private income stream in his dotage: at which point it would, subject to conditions, be taxable as drawn down. Nothing illegal, all within the rules and he would be acting socially responsibly in investing in his future, and reducing his potential burden on the state care system when he can no longer work.
What his accountant is doing is ensuring that your friend is not paying TOO MUCH tax - ie he is paying the correct amount, as opposed to too much through ignorance of the rules. He is avoiding overpaying by structuring his finances within the rules and this may also mean all he is doing is deferring tax.
Avoidance of tax, by definition of the word, is ensuring that you do not pay too much and seems sensible to me. Evasion means paying too little and is unacceptable, cheating, whatever you care to call it. There are fine lines between the two, granted, but if no rules or laws are broken then you surely can have no beef with your friend. Your beef must be with those who create the rules - our parliamentary representatives.
Same thing for people on benefits - there is a fine line between "benefits scroungers" and "benefits cheats" - the former may operate within the rules and make claims accordingly: you cannot throw mud at them for doing it - blame those that create the rules, not those who abide by them and claim legitimately. Again you may not like the rules, so address the rules that allow people to "earn" more by not working.
Your benefits scroungers and your tax avoiders live in the same camp. Your benefits cheats and your tax evaders also inhabit the same moral space as one another. You might not like to see someone stashing money in a pension fund to get the tax edge; I might not like to see a fast breeder single mother having another child to get a bigger free council house. But if both stay within the rules we have to suck it up and address those rules somehow.