V-tubers are dangerous in the same way that video games, television, ASMR, anime/cartoons, digital music, and porn are in that they fry your dopamine system by presenting a sensory input that greatly exceeds the natural norm and making it readily available for consumption. Streamers in general are bad enough with the illusion of friendship in an unhealthy one-sided relationship with someone that will never know you, but imagine how much worse it is when that person can visually be whatever they (you/the audience) want.