When a light enters a dark room, it does not draw upon the darkness to power its illumination. Instead, it cuts through the darkness shining brightly upon the correct path to travel.
The same for the believer. When they come to Christ, they are now the light unto a dark world. They are not to take their motivation, inspiration or power from the dark, sinful world or its different sinful cultures. Instead they are to cut through that darkness and illuminate the correct path to take to salvation