Yes, humans should keep their classification in the animal kingdom. First, it's a basic, scientific fact we are part of a kingdom, animal at our highest level and specie, sapiens at our lowest level of classification. Second, an attempt to separate ourselves from the animal kingdom may have the unexpected consequence of allowing us to believe ourselves above the natural world, when in fact we are a part of the natural world, which we need to protect in order to prolong our own species survivability.
Yes, humans should be considered part of the animal kingdom. Though quite developed and sophisticated, humans have many basic characteristics in common with other animals. For example, humans breathe, eat, and sleep just like any other species. In addition, humans reproduce and will fight when provoked. If intelligence were not a factor, humans would be no different than any other animal.
Although it is generally accepted that humans have a higher level of consciousness and intelligence than most other species, they are still a part of the animal kingdom. It is kind of ignorant and elitist to remove humans from the animal kingdom since humans evolved alongside the animals around them and came from the same starting point.
Humans are part of the kindom animalia, the phylum of chordata, the class of mammals, the order of primates, the genus of homo, and the species of sapien. All of that is code for our genetic breakdown. We are animals because we are not plants, chordata because we have a spinal cord, mammals because we give birth to live young, primates because we are evolved anthropods, homo sapiens because we walk on two feet and have larger brains than our cousins the apes. Being part of the animal kingdom is simply a way of tracking human development and evolution, similar to a huge family tree of all life.
Plants are sort of like animals, but are in a different kingdom level. This shouldn't be any different for humans, either. Do cosmetic brands test on humans to ensure quality? Do you go to the vet for vaccinations? Do you get locked up into a birdcage, only later to be sold in a pet store? If you answered NO to all these questions, the answer is quite obvious and simple.