I too have heard/ read part of the case made by Irwin Schiff et al. Here is the IRS' rebuttal.

When I was a kid in the late 1970s, I joined the Libertarian Party briefly, despite reservations re: their foreign policy. With experience (both that of our country/world as a whole & my personal) I have moved closer to the Center with some Libertarian accent.
I would like to see Dem.s, Rep.s, & Libertarians each control 30--40% of Congressional seats for a while, so that 2 of 3 parties would have to agree to pass any law.

I agree with Alanh above where he states, "There's certainly a valid argument that can be made that taxes are too high, or income taxes are bad policy. I would think the libertarians would be better off sticking to that tack than conspiracy theories that income taxes are illegal."