I don't think that the flesh is necessarily treacherous, evil, bad. It is cantankerous, and it is independent. The idea of independence is the key. It really is like colonialism. The colonies suddenly decide that they can and should exist with their own personality and should detach from the control of the mother country. At first the colony is perceived as being treacherous. It's a betrayal. Ultimately, it can be seen as the separation of a partner that could be very valuable as an equal rather than as something you dominate.