Why do libertarians think that getting your fair share is theft?

Ok, this is an honest question. The capitalist system is set up where one guy has the money and another guy does the work. But the guy with the money gets all the profit. Most people think hard work should be rewarded but in capitalism its the opposite. The rich make tons just by the virtue of being rich but the people doing all the work are left with the scraps. But when Obama wants to make things a little fairer we just get libertatians yell "THATS THEFT". But is it really theft when the system is set up where 1% of the people get 95% of the money and the other 99% do all the work and get the remaining 5%? You call it theft. I call it getting what we are owed.