It is a "paid for entitlement". The money doesn't come out of the general tax receipts. It was not meant to pay rich people.
Your dividend income comments are exactly the sidestep the GOP uses to avoid people paying taxes at a fair rate.
As to capital gains, your statement makes absolutely no sense. Capital gains are paid when a person sells an asset. They have nothing to do with the taxes of corporations. You don't understand capital gains at all.
Let's take this in pieces:
Social security: What does "paid for entitlement" mean? All entitlements are paid for. Whether by tax payers or by debt that is then funded by tax payers. In the current world, because your benefit is derived from your contribution, you could say that social security was not an entitlement. I would disagree because there isn't a direct link between the benefit and the contribution (otherwise it wouldn't be in danger of insolvency in the first place), but that's for another day. For now, if you remove the link that is there by saying that contributions should far out measure benefits for some segment of the population then I don't see how it is anything but an entitlement.
Dividend income: Let's assume a theoretical world where a high level executive works for a firm with a corporate income tax rate of 25%, pays a personal income tax rate of 25%, and there is no difference in taxes between salary and dividends.
For each $1000 of salary, the government receives $0 from his company and receives $250 from him.
For each $1000 of dividends, the government receives $333 from his company ($1333*75%=$1000) and receives $250 from him.
The dividends are taxed more. That isn't sidestepping; that's math.
Capital gains: I am afraid I do. The value of a financial asset is based on its future cash flows. If corporate income was tax free then the cash flows would be larger, the asset would be worth more, and the capital gain would be larger.