You may think it's absurd, but it's not absurd to other people. Gender identity is a thing that someone must decide for themselves, and sometimes it's not a concrete thing. It's not like it affects you, either, so why do you even care? Just let people live, as long as if they aren't hurting themselves or anyone else then it's fine.
I believe people who identify as being gender fluid use it as an excuse/ a way to get attention. It is very hard to believe that you feel like a boy one day and then a girl the next day. I don't believe your thought on your gender can change daily. I feel like it's an excuse to act differently and get things you want. If I would to say I feel like a girl one day, then I could just walk in the girl's restroom or locker room even though I'm not. People who are gender fluid I feel like are crying out for attention. They change their gender in order to have something to talk about and to be different. You can't wake up one day and be different gender have that repeated through your whole life. I do believe that is one way or other. I believe you could be transgender and want to become a girl/guy, but you can't switch daily.
Let's get something off of the table right now: It is not a way to get attention. These people have actual feelings that are valid and in no way fake and should not be taken so lightly. They change their gender identity because gender identity is not a concrete thing, it can be more fluid(hence the term: gender fluid) and is all up to how the specific person feels. Let us also note that there is a difference between gender identity and gender expression. Although it is hard to switch between feeling like a boy and feeling like a girl, that does not mean that it does not happen. All that it means is that it doesn't happen as often. This also does not mean that they act differently, it just means that they identify as something differently. I will not debate the topic of what bathroom/locker room they should use as not only is that a different subject but it is a very complicated one that I am not prepared for at the moment. You also have the misconception that people who are gender fluid switch genders every day; that is not the case. Although it can happen, most of the time they are one gender for a short while and then another gender for another brief period of time. This can last anywhere from a day to several months. Thank you for the debate.