>Why are the Marxists wrong?
Because all forms of Marxism (that aren't just "I'm high on acid and just ate something off of my shoe" crazy) rely on a central authority to do their job, which falls under the problem of central planning.
We've shown repeatedly throughout history that centralized authorities and central planning don't work. This is why Empires crumble, big businesses have to focus on just surviving instead of innovating if they don't lease out parts of their businesses to smaller businesses (it's also the reason you need a board of directors to run a large business), the federal government can't get anything right, and massive numbers of people starve under communism. It all comes back to the issue of central authority and its attempts to superimpose rules and various factors onto local regions for better or for worse- locals know what's best for them, not some guy in China.
The Marxists that don't rely on a central authority to accomplish their ends typically still rely on a violently coercive society. It's never a matter of "you do your thing and we'll do ours" like what is allowed in Voluntarism. It's "my way or get shot/hung/robbed blind/etc." I can not support any sort of ideologically corrupt entity that relies on violence to get its way. That's what children do.
>Why are you right?
I'm not right and I don't claim to be.
What I do claim is that we can show empirically both via direct examples (actual anarchist societies) and indirect examples (the negative effects of government on a society) that my ideology is not coercive, does not rely on violence to make it happen, and generally leaves 95-98% of the world better off (while the 2-5% who are worse off had virtually no worth, and possibly negative worth to society as it is).
>Even if you reduce government power how does that stop corporations from gaining more power?
Who do you think gave those corporations power to begin with? Voluntarist methods have destroyed yellow cab in San Francisco (via Uber/Lyft) to the point where they had to file for bankruptcy. This was a government-enforced monopoly for the region. I know this is hard to comprehend, but A) Large corporations are not necessarily a bad thing, and B) 99% of Large Corporations would FAIL if exposed to an actual market where their lobbying couldn't work.
>What regulations exactly keep corporates in power?
I'd have to cite virtually the entirety of US internal trade regulations. If you point to virtually any industry from the cattle industry keeping us from eating dirt cheap, easily raised, and sustainable buffalo meat, to regulations on specific oranges for orange juice that just so happen to be the kinds Florida's OJ uses, not to even bring up Taxi Medallions… Virtually every regulation has a specific beneficiary for it.
>How do they stifle competition to stay on top in the market?
See above.
>How has government specifically been helping large businesses stay large?
See above.
I literally can't cite every regulation and who it benefits because it would take me my entire lifetime and then some. It would be easier to list off regulations that DON'T benefit specific businesses.