Coker, that's highly insultive from them, and as you know, people don't have much tolerance for yukkuri's arrogance of any kind, this included.
Besides if you let them live usually they translate that as some sort of personal victory, so rather, at least, beat them up a bit for demmanding and claiming i find them attractive.
Telling them you won't give them sweets sweets and that they are butt ugly? (no pun intended)
They'll only whine, insult you and keep arguing, so there isn't much of a point about trolling them in this kind of situations. This isn't like the situation on which the Reimu claimed you could take it easy by watching at her for being so cute and that because of that you should give her sweets. There you have something to work with, here no, you have 2 yukkuris demmanding food for not apparent reason and as much "giving you permission" to fap having the delusional idea that you are attracted to them and that they are making you a favor. Even if you tell them "no i find you ugly i won't fap" it wouldn't be as effective as saying "you told me i could take it easy if i looked at you, but you're damn ugly and i can't take it easy, so no sweets sweets" to that other Reimu i mentioned.
No no no, You pretended to find them attractive, you make them believe that your going to bring them food. But you don't. You come along the next day wearing different clothing and maybe some accessories. You tell them there butt ugly and you give them some food (not much just enough to survive) out of pity for there ugliness. I haven't thought of what to do next but it would keeping this kind of pattern up so that they eventually begin to associate them selves as ugly.
This is an elaborate metaphor for how fanboys sexualizing everything leads to nothing but horror. Pity it's so utterly horrifying it can't get its point across before the viewer scissors his own eyes out.
Kn9, i don't think this is a metaphor of anything, you're looking to hard on it.
Besides, the difference between fanboy sexualizing something and this, is that many times the sexualized something will actually look attractive in 90% of the cases. Only Yukkuri's sexualization bring 100% horror, but sexualization of cartoons, comics, manga or anime? rarely...