I believe that the free market sets prices where they ought to be and does the greatest amount of good for the greatest amount of people.
Unlike previous economic systems such as feudalism, which did feature competition for accumulation, capitalism features competition for profit. Profit can only be obtained in a specific way: by selling a product for more than it cost to make. Now, Marx identified a tendency in capitalism called "the tendency of the rate of profit to fall." In a nutshell, this is the tendency exhibited for all products to become less profitable to market and sell over time. The first business to sell a self-contained ink pen (like a "Bic") made a fortune. But when more marketers of Bic-like pens moved in, the first marketer had to cut their prices to compete. This meant their profit per pen sold dropped. And then one of their opponents came up with a way of making each pen more cheaply, so that opponent was then able to lower their prices. The first business then had to cut their prices, too, and made even less profit. And this tendency applies across the economy to all products.
For the maker and seller of a product, there are ways to avoid this inevitability for a time: (a) you can find a new audience to sell to that is not already saturated with the product and can be charged a higher price; (b) you can find a way to access some new, untapped supply of the raw resources you make your product out of, allowing you to lower your overhead and make more profit per unit sold; (c) you can find a way to switch your manufacturing to incorporate laborers who will accept a lower wage than your current laborers.
The fact that capitalism demands that everyone compete for profit or else get outcompeted and bought up means that anyone who does not incorporate some of these strategies will get "eaten" by someone who will use them. And this eat-or-be-eaten logic of capitalism works at the smallest level and the large, because each country has a bloc of capitalists who must compete with all other countries' blocs of capitalists. This means that in order to avoid being put in some other country's thrall, each country has no choice but to try to be as colonialist/imperialist as possible or else it will get outcompeted by whichever countries will do that.
This means that, historically, capitalists have always supported and pushed for expansion into other countries to try to take their resources as cheaply as possible and incorporate their people into the workforce at as low a wage as possible. As capitalism spread around the world, this is the logic it has always obeyed. The system made it inevitable.