Obvious trolling is obvious, but okay, here's your answers:
-Adaptation Standpoint: If I adapted Lord of the Rings, with the sole difference being that all of the hobbits are gay, people would logically ask why. It's a random change that doesn't change much and only raises questions that are presumably never answered, so people would logically ask why make the change in the first place?
-In-universe Standpoint: Why would an entire species be all gay? Hobbits are relatives of Men, so even casting aside the obvious questions as to why and how such a drastic shift occurred, how are hobbits meant to reproduce? I guess it's technically possible, but presumably every hobbit would loathe coitus. And speaking of which:
-Biological Standpoint: Hobbits are related to Men (humans), we know how multicellular animals, mammals included, function, and that includes opposite sex animals reproducing through opposite-sex pairings. So either your hypothetical homosexual hobbits are an exception to this (having some other means of reproduction), or have evolved in such a manner where such a process is distasteful, which doesn't make sense in evolutionary terms.
So, yeah, making the hobbits gay would be weird. Frankly, I think the larger ball is in your court is to explain why it wouldn't be.