I fail to see where making a living from book sales on any subject is a problem. While it's unfortunate that this individual was admittedly guilty of fraud, why does that mean it's wrong to profit from the Bigfoot phenomenon? If there's an interest in the subject matter, and he authors books on the subject, why is it wrong for him to profit from it?
Fraud is wrong whether you're a Bigfoot proponent, a skeptic, a plumber, or an accountant. Would you feel better if he was found to be guilty of fraud without making money on Bigfoot-related topics?
He failed to report income while collecting SSI. Does this somehow invalidate what he's written, or does it make it wrong to profit from it?
Failing to claim the income correctly is the issue here, not how the money he failed to report was made. Besides, it doesn't seem to me that he profited exceedingly from the topic.