To Mr McGee,

потворствовать is a formal or bookish word for 'let happen something viewed as immoral, or being too liberal, show indulgence towards something viewed as undesirable or immoral by one the parties involved'.

it is very and very close to the meaning of 'turn a blind eye to' or to cause further spread of something bad by inaction and lack of response...

Example: Не заявляя о пропавших вещах, вы тем самым потворствуете распространению воровства в этом районе (awkward example, but the idea must be clearer now I guess). Can be transl. as - By not informing the police that something has been stolen from you, you cause further spread of theft related crimes in this disctrict.