Demisexual is default to zero attraction until a strong emotional attachment forms.

I believe asexual people exist (people who are never sexually attracted to anyone). Your definition of demisexual here though is very broad and would include many heterosexual, homosexual and bisexual people as is not that uncommon for people to be unable to feel sexual attraction until they have a deep connection with the person in question.

grouping bisexuals and homosexuals with asexuals and those who fall under the asexual spectrum a.k.a. demisexuals is kind of insulting for everyone involved. Especially the homosexuals, because no amount of emotional bonding is going to make a lesbian ok with dick or a gay man ok with pussy.

Your definition of demisexual, defaulting to zero attraction until a strong emotional attachment forms doesn't imply that the demisexual person would have to be pansexual, okay with all genitals as long as the emotional bonding is there. For some people the emotional bonding and the person being of the right sex are both requirements for sexual attraction to be able to kick in.

If you don't want demisexuals to be grouped with heterosexuals, homosexuals and bisexuals then you should narrow the definition of demisexual so it no longer includes people who are able to experience attraction. If you only exclude those who experience attraction pre deep bonding then you will inevitably categorize some heterosexuals, homosexuals and bisexuals as demisexual too.