Tyler Cowen's Inevitability Argument

I'm intrigued by Tyler Cowen's line of argument against social security personal accounts. The argument, as far as I can see goes something like this:
(1) Even if you have a program of personal accounts/forced savings, political reality will still lead to a secondary safety net for the elderly.
(2) A program of forced savings plus a redistributive safety net (welfare program) is worse than just a safety net.
So, (3) Let's make social security into a welfare program for old people who need it, and just forget about the personal accounts/forced savings.
Tyler's argument turns on his claim that there is simply no way to get around the fact that we're going to have some form of redistribution to the poor among the elderly. I am, however, not certain why Tyler is so positive that we're stuck with some kind of welfare for the old.
It seems to me that the underlying assumption of Tyler's argument is that it is impossible for the state to credibly commit to a scheme where individuals are responsible for their own long-term welfare. Perhaps if the state could so commit, and people really expected that they would sink if they refused to swim, then they wouldn't take out huge loans against their personal lockbox accounts, and they wouldn't upon retirement open their lockbox, burn the money, and expect to get bailed out. But the state can't so commit, and so we're going to get a moral hazard problem anyway.
In other words: If people think they'll get welfare, they'll act irresponsibly. But if you try to tell them that they won't get welfare, they won't believe you, and they'll still act irresponsibly. Because they've acted irresponsibly, they'll need welfare, and because they need it, they will get it.
I wonder if Tyler would agree that this is the underlying structure of his argument?
Now, I'm not sure what to think of the inevitability argument. I'm pretty sure it's good rational choice reasoning, but that certainly doesn't make it true. I have some conjectural thoughts on why it may not be true, which I will share soon.
[Cross-posted on Crescat Sententia.]