If ZOS doesn't want to implement a coded solution, I can understand that. But some action needs to be taken. It's clear that this is way beyond social norms by the fact that only ONE guild leader pushes this form of "recruitment."

It doesn't seem like a grey area to me at all. No means no. If someone declines a guild invite, repeatedly sending that same person another guild invite every time they go to certain wayshrines is harassment and already against the TOS.