[pdpi]

The OP said "I'll side with the cynics" and then justified this by describing how they thought the device would operate — by detecting the plasmodium itself — and how they thought it was impossible.

The article, however, explains how the actual proposed means of operation is based on measuring actual symptoms of the illness — observable changes to the red blood cells — which is at least somewhat compatible with the mechanics of a pulse oximeter, and, therefore, not entirely unreasonable.

The tone was harsh not because of the cynicism, but because said cynicism was based on a concern that wouldn't even have been there if the OP had RTFA.