Would, say, transferring my 401(k) to a Roth IRA safeguard it against this kind of crap?

You’re safeguarded anyway. What these assholes are proposing wouldn’t force you to give them your money, it would however let you make the bad decision for you to give them your money. In short, they haven’t gotten your money and even if they get the rule change they want, its still your choice to give it to them.