If you think that capital gains should be taxed just like ordinary income then ask yourself this...
Lets say you buy a house for $150,000 with a 30 year mortgage. 20 years later you have paid say $250,000 with payments and interest. Lets say your house has appreciated (because of inflation) in that 20 years and you sell it for $250,000.. The government says you just made $100,000 and wants half of it for taxes.
Does that sound fair to you?
It sounds perfectly fair to me. The reason we allow a primary homestead exemption is not because it's "not fair" - but because we want to encourage residential mobility.
We could have an entire thread on this, but allow me to ask: what societal interest is being fulfilled by treating investment earnings in a tax preferred manner compared to funds earned at a job?
Are we trying to instill upon our society that your goal should be to not work and live off of investment income instead?
If your goal is to encourage direct investment that creates jobs, the tax code should be tilted to put direct investment at an advantage to investing in the secondary market. Again, remind me, what purpose are we serving by giving tax advantages to secondary market gains?
Taxation, at it's most philosophical level, exists to accomplish one of two things:
1) Fund the operations of the taxing body
2) Incentivize/disincentivize certain behavior
You can't make an argument for (1) in this case, not even from the perspective of the Laffer Curve, because Direct Investment creates jobs - not secondary investment.
So that leaves us with (2). What interest to we have in rewarding passive financial gain over other forms of income?