Does Satan only promote obviously sinful skid row behavior?
No. Satan is not limited to promoting obviously sinful skid row behavior. He will also promote beautiful, cultural, and enlightening things, using whatever works to keep people from the truth. His aim is to turn people from the truth, and he does not care what instrument he uses to do it.
Les explains that believers are up against two spirits: either the Holy Spirit or the evil spirit. Satan has his demons, and this satanic power is what the world is up against. But Les warns people not to think that all Satan can promote is what we would call skid row behavior. Instead, Satan will promote the most beautiful things and that which people think is cultural and enlightening, as long as he can keep people from the truth. He does not care what he uses. This fits the warning in 1 John 4, where believers are told not to believe every spirit but to test the spirits, because many false prophets are gone out into the world. Every spirit that does not confess that Jesus Christ is come in the flesh is not of God, and this is the spirit of Antichrist already in the world.