Of course that's unfair. What business is it of the state what money I make? After all, I already pay a bunch of taxes on my salary every month! Or does the state also support me if I make losses and then give me money? I doubt that. This is my property, in which I have invested more than enough (taxed money), so my profits are none of their business!
Because speculative gains are a kind of income. And they are to be taxed like any other kind of income. Although, since a certain SPD minister, they are taxed at a flat rate, so still far too little. But don't worry, two years of owner-occupation (on paper) are already enough to evade this tax.