Perhaps you should have read the tax law before contributing to your 401K if this really concerns you!
401K plans (and their various cousins such as 403B and others) have always been TAX DEFERRED, not TAX FREE. The value of these (as well as "traditional IRAs") plans is that you are able to reduce your taxable income while working and contributing then, when you draw the money out in retirement, you (typically) are in a lower tax bracket.
There is no free lunch here!
The ROTH IRA (and its cousins) is a different breed in which you don't get any tax benefits up front but when you draw the money out in retirement it (for now at least) is totally tax free (including whatever the account earned over the years).
Save you outrage for the day that the guv'mint institutes a "wealth tax" to pay its mountain of obligations! At that point it will renege on prior promises not to tax ROTH IRA benefits. Also, at that point, your 401K contributions will probably be taxed at a much higher rate than the rate in effect when you made your "tax deferred" contributions!
That's why I like the ROTH IRA. Getting past all the analysts hand-wringing about figuring it out, the simple fact is if I can pay the tax on something now and I'm guarenteed that BigBrother can't finagle how I'm taxed on it, that's to my advantage.
I would think it would be easier to justify changing the rules on taxing deferred accounts, where people haven't met their obligation.
A really out-of-control government would take a percentage of accumulated wealth in those accounts or add another expense to an already-paid obligation.