first, let me state a principle that hopefully you will find logical.  and some background first.  Investments are a big part of what drives a capitalistic society--actually any society, socialist as well.  Factories have to be built to produce goods, and that requires investing money in them.  The same for investments of R&D.  You want people to make the choice to take some of their money, and rather than spending it today, invest it in the future.

Take that a step further, you would ideally like them to invest in businesses, or in factories, that are going to do well.  It's not so much that you want that investor to do well, though you might,,,,but more that he invests in good businesses that will grow, produce jobs for the local economy, be competitive on a worldwide scale,,,,,etc., etc.--be good for society.  

Following that idea, you would like investors to be able to move their investments into those industries that are growing, and where their investments might create wonderful businesses that would compete effectively in the world, provide wonderful products for the world, but also create new high paying jobs for the local economy (or maybe the country, like the US, France, UK, etc.).  Create businesses that have long term competitive advantage--technology companies in the US, and medical device companies (make angioplasty products) might be good examples.  

So you want investors to be able to move some of their money from the older investments, into the new future--and of course there is risk for them as they do it, because you're never sure the "new" will be successful.  Investing always has some risk, along with great opportunity for gain.

So let's say you were an investor in the 1900's, and you had been wise enough to invest in the auto industry.  You put $10,000 into the auto industry, and it was a huge winner and you stuck with your investment for 25 years,,,it grew to $10 million.  The auto industry still looks good (no one back then saw the wipe-out coming from Japan), so you're getting dividends every year at 3%,,,,$300,000,,,you can sell a little stock along the way for new cars or whatever.  But you're a pretty happy camper.

but you see this new thing--integrated circuits, computers.  Sounds a little crazy back then, certainly risky,,,,,but could it be another "auto" success?  You are tempted, and you think of taking $5 million out of your auto investments and buying Intel, or Apple, or Wang (whoops), or IBM, or a little of all of them.  But you have to sell $5 million of the auto investment to buy $5 million of the computer investment.  I think the ordinary income tax was 50% or so, and the capital gains tax was 40% or so back then.  so to sell $5 million of auto stock, for which you had paid $5,000 (half the original investment of $10,000), you would have to pay a capital gain tax on $4,995,000,,,,and at a 40% capital gains tax rate that would be a tax bill of $1,998,000, and let's round to $2 million to make the rest of this easier.

So one choice is to pay the government $2 million in taxes (lowering your net worth from $10 million to $8 million), keep $5 million in autos and have a new investment in computers of $3million.  The computer stocks need all the money they can get to grow, so they're not going to pay any dividends,,,,so you're annual dividend income falls in half,,,$150,000, not the cushy $300,000 you had.  You've watched these computer stocks,,,you know they are risky, but have a huge potential  payout if successful--but it's nerve racking as they drop 15% then go back up 20%, etc.

But the other choice is to stand pat,,,don't sell the auto stock,,,keep your net worth at the $10 million level,,,,don't pay $2 million in taxes,,,,and stay with the good life.

So it is not a clear choice,,,back then,,,,(now we know, in retrospect the right decision).  but you can look at it as the investor having a choice of paying 0 taxes, by just keeping his auto stock.  Versus paying $2 million in taxes, and changing his investment structure.

I would argue that from a society standpoint, we want strong incentives for investors to be willing to take risks,,,,and move their investment dollars into some of these new things.  With investment dollars going into a lot of new things,,,some turn out to be big winners--new jobs, competitive advantage for, in this example, the US.  But also many of those investment dollars turn into nothing, because many new things don't work.  but, this is what drives growth.

so, when I put on my hat of wanting our economy to do very well on the world wide stage, I say something like the following from my comment:

But this is a case where the benefits of not having constraints on the movement of capital, so that capital goes to the most promising investments, has definite positive impact on all income classes--imho.

I feel rather strongly that low capital gains taxes are necessary for a robust economy, as I've commented elsewhere on this thread.

But, I admit that when I think about wanting less variation in income distribution, this doesn't help, thus the comment

But if you have low capital gains, it does mean more after tax income for the wealthy, who tend to own the assets--so it works against income distribution goals.

Two different perspectives that need to be balanced into economic growth policies, tax policy and income distribution policies.