I lived through a violently abusive relationship for three years. I also initiated the relationship by kissing him for the first time, and I'm pretty sure I also initiated sex the first time we had it. Does that now mean that I wasn't abused? That the violence and emotional abuse he put me through doesn't count, because hey, I started it!
Who initiated what has nothing to do with anything. Just because Buffy initiated a physical relationship, that doesn't mean that Spike had the right to continually touch her without her consent after that (which he frequently did).
While my history with abuse doesn't make me an expert on the matter by any means, it does mean that I recognise abusive patterns in fictional relationships, often because they trigger me. It also means that I have a certain understanding on the mind-frame of abuse victims.
If I had had the strength, I would have beaten my "so-called" abuser within an inch of his life for what he put me through.
Also, telling Spike he's "convenient" is hardly abuse. She isn't trying to isolate him, she isn't trying to degrade him. Spike isn't suffering debilitating mental illness during the relationship. They aren't on equal ground during Season 6 and Buffy is clearly victimized by Spike throughout the entire season.
I feel for Buffy because I was abused as a child, I did not tell anyone , I let myself be put into a position where it could happen again , i did not stop it happening to me when it was happening.....Why ? as Buffy I have no idea , mine only stopped when I was injured and needed medical help , Buffy's stop when she was mentally strong enough to stop it
So many parallels to myself and the abuse Buffy suffered at the hands of Spike , Spike is taking advantage of a mentally ill Buffy, I see it , I feel it ,