Amazing how much our experiences influence how we respond to a fairly simple question. I guess that some people have encountered really nasty toilets and others have a long history with really nasty bugs and whatever mental image is triggered by the question sort of influences the initial choice. Then, of course, after the fact justification narratives get created.
For me, "cleaning toilets" is rather civilized: not too nasty, toilet cleaner, brush, flush, presto and its done. Opposing that to killing bugs is a no-brainer since I frequently rescue certain bugs and release them outside. I expect that if the toilets were really super nasty, I'd go for the cold water shower.
Some people appear to have some pretty traumatic images in their heads about bugs and that can condition their response to some extent.
The most interesting responses are, of course, Luke Wilson's and wmu9's. Not only do they want to kill bugs, they want to make it the RIGHT choice, the moral choice which requires that they make the choice to not kill bugs, to prefer to clean toilets, wrong and bad and they've put some energy into this narrative.
Personally, I don't think the experiment is all that good of a way to weed out sadists from the population because of the focus on bugs which are generally pests to about everyone so certainly, many people are going to think "kill bugs? yes!" without further ado and without having sadistic tendencies. When they learn from the article HOW the bugs will be killed, they are turned off and change their minds. Normal, I think; especially if you have "bug trauma".
In the context of "The Work" and people who are studying awareness and so forth, it is interesting in other ways: who overthinks, who can switch into "beginner's mind", whose fundamental instincts are for service to others, whose System 2 goes into overdrive to narrate a choice? etc. For most, it seems to have been a useful question just for initiating some thinking and self-examination.