Before beginning, understand that the free market and capitalism are not
the same but are closely related. Capitalism refers to creating wealth and owning capital, production, and distribution. The free market system involves the exchange of wealth or goods and services. I don’t see how one exists without the other.
The top 10% of income earners contribute significantly to federal income tax revenue, paying either 71% or 76%. Yet, debate continues on whether this distribution is fair or whether reforms are needed to address wealth inequality.
The free market encourages competition, innovation, and efficient resource allocation. It also allows businesses to respond quickly to consumer demands. Compare this to communist regimes, past and present.
People have the individual freedom to choose what to produce, buy, and sell. This gives us entrepreneurship and personal initiative. Again, compare this to past and present communist regimes.
The kicker is a free market generates wealth by promoting economic growth, job creation, and investment opportunities. This means that while creating jobs, there is a financial risk, which equality advocates want to ignore.
So, we arbitrarily take from those who can best afford it and give it to those most in need. 
This is Marxist Theory 101: “From each according to his ability, to each according to his needs.” This has failed time and again throughout history.
The free market system dates back to William Bradford. The communal system failed by making those unwilling to work to be non-productive and take from those who produced. The colony was dying, so Bradford experimented with giving people private property rights to produce and earn. The colony flourished under the new system.
What is there to debate?