tDCS modified moral behavior! By ‘utilitarian’ I believe the researchers mean that the subject was less likely to ‘save the many’ by (actively participating in) sacrificing the few.
Accordingly, during anodal stimulation of the left DLPFC participants rated the utilitarian actions as more inappropriate than they did during sham and cathodal stimulation. Thus, anodal tDCS of the left DLPFC resulted in a shift of preference from an utilitarian, active decisions (i.e. to actively hazard another person’s life to rescue the lives of several people) to non-utilitarian, passive decisions (i.e. to avoid harming another person, but in consequence to accept the harm to several people.
For context, you might want to examine The Trolley Problem!