Where does capitalism mandate corruption? Yes, it is not realistic to assume there is no corruption, but capitalism in and by itself does not mandate corruption.
Obviously this all falls apart when capitalism can buy legislation. We are seeing how the USA is currently eroded by a few oligarchs.
"capitalism" was meant to harness the greed in men- they're self-assembling groups on mostly level playing fields, and the people vote during every purchase. The more votes they get, the more opportunities to expand. Only when the people fail to choose wisely is a governmental body supposed to come in and help "regulate". The other option is the government decides from on-high how things should work, and you'd better hope that what got them to power was good. Then these people need to be wizards at allocating labor, research, and benefits.
Anything that involves humans will have corruption.
Society needs somethings to try to stop corruption wehther government rules or non government actions.
Under pure capitalism what stops this?
capitalism definitely mandates corruption
non-corrupt competitors will be beaten every time by corrupt ones
They're not saying it 'mandates' it as law, but that the systematic incentives inevitably lead to corruption. The ability to buy government is irrelevant - this is just the easiest method right now of converting money into power. If there was no government to buy, private business would execute that conversion themselves by ruling over people and enforcing their wishes directly.