Intuitively (dare I say logically), this concept appears to be a logical fallacy. Is it actually a "formal" fallacy and does it have a name?
Reincarnation must be true because I wouldn't want to live in a world where this is all there is (and anything goes etc.)
Theory X must be false because if it were true, well that would just be sad
In other words, conflating the essence of the idea with notions of its consequences that have no bearing on the veracity of the idea itself.