Well, this example is especially sordid. I suppose that's why it hits home. Something similar happens whenever the subject of family or familial obligations comes up these days. People will rant and rave about what a "burden" (the usual word) marital obligations and children are: HOW DARE THEY TRY TO TIE ME DOWN! But they tend to get queasy if you propose butchering kids and eating them. There are limits, in other words, but they are limits to which our sensibilities soon grow inured unless they are restrained by the kind of moral principles most people used to profess.
Not wanting to be married after the left has destroyed the essence of the family is a far cry from killing your parents off.