Comic relief character traits aside, this unfortunately captures the mindset of Japan and homosexuality. Gotta remember that Japan is a very conservative country; old to the school! Anime and manga will make it seem normal, funny, or whatever else but the actual Japanese frown upon it and are not ashamed of cutting out family over it. It's gotten better over the years but when you compare it to more open-minded countries like the US, Britain, France, etc. it's still pretty bad. It sucks, but this is considered normal thinking over there.
Also the "chemical castration" was not intended by the MC (there's a reason the chapter is called "Handle With Care"). The sister pretty much OD'd the brother with medicine in her zealousness despite the MC telling her exactly not to do that. Tragically, the lesson about overdosing on a medicine went to the wrong subject, causing the controversy when this chapter first came out. Gotta remember that the medicine was meant to be a tranquilizer for his raging libido, not as a "cure for homosexuality" as some think the author intended. But like any medicine, the cure can become a poison when it's overused. This was a good example, but it went to the wrong subject, causing the earlier mentioned controversy.
Put simply, while this chapter can be offensive, it was not an ad against homosexuality. It was a warning about overdosing.