They still should be able to express their ridiculously misinformed choices.
I think you're arguing for mandatory voting? So you don't want them to be able to vote, you want them to be obligated to vote.
And what if their ridiculously misinformed choice amounts to them voting for "Newt Gingrich" because Newt sounds like a cool name?
I don't really get what is gained by having that opinion expressed?
But this kind of misinformed vote is marginal. Most "misinformed voters" more or less vote based on some kind of issues, even though they don't really grasp the specifics of these issues. In short, they do have opinions on stuff, and if we are a true democracy, their opinions should be taken into account regardless of what we think of them.
If they care so much about those issues,why do we need to make voting mandatory for them to bother voting?