Explosion said: ...or maybe its the fact they are being forced to eat their own mother and they aren't shitheads so the "DO NOT WANT" of the situation overrides their preference for sweet things.
Kind of like if you were to hypothetically really like the taste of raw meat then you were mind controlled into eating your own mother you probably wouldn't find meat so tasty anymore.
True, they are not shitheads, but I don't believe they are niceheads either.
man tells them that there are sweets right there, but the yukkuris look and can't see any. Of course he is talking about the yukkuris themselves. They start calling him stupid and moving towards him...
Well they do start asking (maybe even demmanding) sweets sweets to the humans for just, well, "showing up" even before the scientist tells them "they" are sweet sweets, they could be average slightly siding to scum in the best case or mid tier scum in the worse case.
In the end it may not matter much, since they were made into cannon fodder and guinea pigs for SCIENCE.