Seems like at the crux of this lawsuit, isn't that Amazon is selling products they're legally allowed to sell, it is that Amazon is also selling a booklet with information that is readily available online telling people how to use that product in unintended (deadly) ways.
HN hates Amazon, HN also hates censorship, the question is which do we as a community hate more? Should a company be liable for the free access of information? There's even some people in the comments already calling for new age restrictions on Amazon accounts for certain products, I wonder how long once that is implemented before certain localities pass laws restricting access to "unpure" materials like sex ed/safe sex?
I won't even address the "suicide kit" claim since that is simply sensationalist reporting. Ironically I think if this lawsuit is successful on its merit, you could also sue arstechnica for promoting the same thing they're accusing Amazon of. That's the nature of censorship, nobody is really safe once you open those floodgates.