My personal intuition is that what is 'rational' depends exclusively on your objective function at the time you make the choice.
I may value $10, and avoiding eating bugs a lot; if you offer me $30 to eat a cricket and a pill that gets rid of my sense of disgust and makes me care about money exclusively, I wouldn't take that deal because until I take that deal I still want to avoid eating bugs. That, were I to take that pill, I would no longer regret the decision I made, is not that interesting. If on the other hand I dislike eating bugs, but...
I think the conclusion is 'repugnant' because people don't want to admit the extent to which they are anti-natalists.
There is a big proportion of current lives that, if I could instantiate an infinity of, I wouldn't think it was a good thing. And the 'repugnant conclusion' is just them realizing they actually feel this way when asked if they would like to shut up and multiply a negative number by infinity.