The main argument against Capitalism is that, if left unchecked, it will lead to concentrated power in the hands of the wrong people. However, some of our best economists argue that, if we don't fall pray to the early conclusions , we'll find that capitalism is, probably, the most humane systems we know.
I'll leave here the following video of Milton Friedman explaining his position on this matter. Let me know your thoughts:
https://www.youtube.com/watch?v=27Tf8RN3uiM