The humor is shown in the way the trials were conducted; First of all, they were advertised - like an entertainment spectacle or a circus show.
These witch trials are ridiculed because they are referred to as an Experiment - supposedly based on facts and reason to prove someone is guilty, and alluding to science experiments - when in reality they were not logical at all.
In the end they decide to repeat the trials, and they promise nudity to attract a bigger audience.