For humans, homosexual behavior is not considered normal for several reasons. First is Christianity. Please be aware that I am not hating about Christians. I have many friends who are Christian including my best friends. I am just stating my opinion. Religion no matter how you look at it is started from humans. Many heterosexual people see homosexual behavior as abnormal because homosexual behavior does not result in offspring and sex is for offspring. The pleasure is an enticement to have more sex and therefore have a greater chance of keeping the human race alive. Also, more people are heterosexual than homosexual, so people get the mentality “Everyone but a few are heterosexual therefore being heterosexual is normal.” Then, those people (let’s be honest, most people back then do not think that homosexuality is normal) include that in their religion that spread to others who grow up believing in that religion and therefore homosexuality is abnormal. Christianity is what I mentioned because it and its other branches is the main religion of the world. Second is male pride. For two men to have sex, one male must “submit” to the other male. This will chafe at many men’s pride as “submitting” means being weak and therefore a females as females are supposed to be weak and submit. (This is meant to be an insult to females as I am one, but this is just what the cavemen in men think.) Other makes when then see the “submissive” men as weak and outcast them from the group as if there’s a weak man among them that’s a weak link that may get them all killed by the saber tooth tiger. Please note that I am describing the baser instinct in men. We see this in Ancient Greece. They viewed the one penatrating as superior and masculine and the one receiving as weak and feminine. Gender was not as big deal back then. It became a big deal with the spread of Christianity. My male friends all express the same opinion when I talk to them about this. The reason I didn’t include female pride is because I just don’t know enough to support that conclusion. However, in animals, homosexual behavior is completely normal as seen with probably the best example bonobos who have sex with other bonobos regardless of the gender. All in all, only humans probably view homosexuality as odd as humans have the ability to do critical thinking that other animals can’t. Please note that this is merely my opinion and not me spreading hate about others. Hope this gives you some food for thought. If you reply, please give me a reply that’s constructive, logical, and gives me food for thought. I will ignore haters.