The old Dr. Charles scene doesn’t make any sense

In “Old,” Time is against the characters literally as most of them will die within 24 hours if they can’t find their way to the sea. Luckily for them, they had a doctor with them. It’s correct? Wrong. Usually, having a doctor on the team is great, but this doctor does more harm than good.
Dr. Charles (Rufus Sewell) suffers from some form of mental illness, presumably schizophrenia based on the delusions he experiences at the end of the film. He also carries with him some racial biases, as seen when the group discovered rapper Mid-Sized Sedan (Aaron Pierre), a black man, on the beach, and Dr. Charles demonstrated. some racist behavior towards him. This was further developed when, after signs of his mental illness further developed, Dr. Charles cut the medium sized Sedan with a knife. Thankfully, the Mid-Sized Sedan rebounded instantly from beach time, but here’s the big question: Why hasn’t anyone taken the knife from Dr. Charles? The other characters just leave him with the weapon.
Most people would think to confiscate the knife from the unwell doctor, but these characters don’t, which eventually leads to Dr. Charles murdering the mid-sized Sedan. Now, the reasoning here could be that the movie offers some commentary on how different people react in these situations, as well as the fear of running out of time in our lives. Either way, it was still hard to ignore the option for him to keep the knife.
https://www.looper.com/754226/the-dr-charles-scene-in-old-that-makes-no-sense/ The old Dr. Charles scene doesn’t make any sense