Public fundraising laws exist to protect the average Joe from losing his life savings to fly-by-night hucksters while trying to ensure companies can still raise capital.

If you're a wealthy/sophisticated investor, the expectation is that you're already capable of assessing investment risk on your own (including, if you think necessary, getting your own lawyers, direct access to a company's financial reports, due diligence, etc). Average Joe, on the other hand, is required to be given audited financials, a prospectus that's vetted by regulators, explicit statements of share rights, etc etc.

Not sure why you brought up lying, that's totally different (and still illegal, public or private).

The difference between raising public vs private money is whether or not you are legally required to actively disclose your financials/risks/business plans/etc. I can (legally) raise money from a wealthy family office with nothing but a phone call (basically how most angel investments work). I can't do the same if I'm trying to raise money from a random Joe off the street, that will land me in jail.

Correct, this means anyone will be able to buy/sell shares on the open market.

It's also why the financials are actually open to the public. They have to publicly disclose all financials/risk factors/etc before they invite the public to buy shares The idea is that institutional/wealthy investors are savvy enough to figure that out on their own.