One way is to educate people about the importance of respecting others' privacy and dignity. When we understand that celebrities are also people with feelings and rights, we are less likely to create such inappropriate fantasies. Also, media and social platforms can play a role by promoting positive and respectful content about celebrities instead of allowing or encouraging any form of inappropriate stories.
Firstly, we need to have a strong moral compass. We should always ask ourselves if what we are thinking or creating is respectful. Secondly, we can promote a culture of positive fandom. Fans can support their favorite celebrities by celebrating their real contributions, like their charity work or their influence in promoting certain positive values. By doing so, we shift the focus away from any inappropriate or disrespectful 'fantasy' and towards a more positive and respectful relationship with celebrities.
We can focus on their work achievements. For example, if it's an actor, we can talk about their great performances in movies or plays. This way, we keep our attention on positive and respectful aspects of their public personas.