Back when I was in school, I am a multitasking monster. I play games while eating and talking, I work on assignments while watching Netflix (I don't know how I did that) and my favourite multitasking activity:
Reading while listening to music, talking with my friends and eating all the same time.
But then I took a course on psychology and my professor told me that multitasking is not efficient and results are often less productive. In terms of cognitive functions, it reduces social awareness and memory retention since your brain can only focus on one thing at a time. In short, multitasking leads to breadth instead of depth activities. Since then, I started to reduce multitasking.
I found that I can focus for longer periods, work on assignments more efficiently and pay more attention to detail in my work and surroundings. The highest level of multitasking I do now is probably just listening to music while working. In conclusion, I'd say yes multitasking is evil, especially for software engineers who often has to focus and work efficiently for a long time.