JWs are constantly warned of the danger of associating with worldly people. They use the scripture, "bad association spoils useful habits."
They must have some association with them during work or school hours, but they avoid unnecessary association with them after hours.
They view worldly people as essentially "unclean" and as a threat to their spirituality and relationship with God. However, they also view them as possible converts to whom they are obligated to preach so that they have an opportunity to learn "the truth."
Since they are not worshipping Jehovah they are serving the interests of the Devil, but they aren't necessarily Devil worshippers.