First, the Radical Personal Finance guy is a little, shall we say, out there. Definitely on the prepper/doomsday/paranoid side of things. Unrelated to this topic, but he also has some anachronistic ideas about the role of women. That's when I stopped listening (and I'm a guy).
Second, the protections offered IRAs are state dependent. It's irresponsible of him to make a blanket statement like that. Find out what the creditor protections of IRAs are for your state if you're worried.
Third, how worried are you really about creditors? I would say the guaranteed cost of paying tax on the gains in after tax is greater than the unlikely cost if you're sued and lose your IRA. Get good insurance to cover liability (auto, homeowners/renters, umbrella), don't take on debts you can't afford, save the max in all tax advantaged accounts regardless of creditor protection, and get on with life.