Why taxing capital income is unfair

Is it fair for two people with identical opportunities to pay different amounts in taxes over their lifetimes?

Consider two individuals – call them Mr. Spender and Ms. Saver. They have the same job and the same qualifications, and they each earn $100 in wages today. They pay tax on that income – let’s say the tax rate on wages is 20%, so they’re left with $80 each after taxes. Both face the same choice: Spend the entire $80 today or put part of it in the bank and let it earn interest.Notice that there’s no inequality here.