I think his 50% tax burden number comes from including Federal income and payroll taxes, State taxes, and local taxes.
That's probably correct only for highly paid professionals that get most of their income by selling their skills. Anyone with income that comes from wealth isn't paying anywhere near that.
The tax code in the US at all levels is incredible stupid.
But the 50% number isn't connected too terribly much with the lack of hiring, though. If you ask a business people why they aren't hiring many will tell you that they just don't have enough time to both run their business and worry about all the extra bureaucratic hassles that come with employing someone -- that might include paying some taxes, but it also includes liability and regulatory concerns.
Employing a new worker is like walking through a minefield. You might have seen job advertisements asking only for those that are currently employed. This is an attempt to avoid all those disasters that come with hiring the wrong person.