People who CAN lower their tax rates are most arduous proponents of low capital gain taxes. They constantly cherry-pick from pure economic theory to influence policy to their advantage.
Income should be taxed equally, and progressively, period.
Capital should be encouraged to be invested smartly, not lightly taxed when gained. The major flaw of this theory is capital accumulation leads to economic prosperity for everyone. Efficient capital investment leads to it.
If I can convert part of my salary from income into capital gains there is no benefit for the society, since I produced exactly the same amount of GDP. I thus take a small share of the NHS expenditure (otherwise funded by HMRC)and buy an ipad. Even better - a new house in Kensington since their price will never go down... Where is the net gain from lower capital tax?