I think the season 6 was needed in order to show how both of the characters matured, and grew on eachother. Sure I didn't like Seeing Red..but I thought it was a turning point..a very important point. It showed the best and worse of what love can do to a person, it can bring you the most joy, or it can completely destroy you, if you LET it.
I thought it was really interesting that when Spike came back in the beginning of "Beneath You", how Buffy didn't seemed to pissed at what he had done...it was almost like she wanted to put on this little show to keep satireboy(xander) and dawny at bay..you know from nosing about their little relationship.
Well if you play it back you'd..notice the pretend annoy look..she actually looked happy to see him. Another thing I think in seeing red in the past episodes she had not really trusted him or herself,and when theyhappened it must have brough into prospective how much of a bi**h she was to him, I think of course she was hurt by what he did, but she finally realized the awful turn that it had taken..not sure how to explain it. but the expressions in that scene she had was obviously hurt, but also like wtf have I done?
Which explains why she so easily forgave him in the beginning of season 7.
If you remember she says "I could never love you." Maybe I'm digging to deep. but I took the beatings she gave him as "I don't want you to love me, I'm horrible I DON'T deserve it. I hate you for making me see I'm not such a terrible person. I've made mistakes..blah blah.." I think in s6 she hated the fact that he made her believe she was more then a slayer, more then the average girl. I don't think she wanted to believe she was worth something..sometimes it's more harder to love yourself then anything.
Okay..so back to seeing red.
If you remember she says "I could never trust you enough for it to be love."
I translated that as "I can't trust myself to love you." once again brings bac k how she treated him. And the whole bangel, and briley relationship, and sleeping with parker. The first two she really cared about, she trusted them, and they all betrayed herself.
also when she had said "I could never trust you enough for it to be love", I also took it as her trying to convince herself she didnt love him, and that she didn't deserve to be loved.
Lol, lastly..because I'm ranting too much...
when she referred to him as being a monster.
Right away, it clicked and I noticed how much she emphasized that word "MONSTER", "THING". I thought she is talking about how she feels about herself. If you noticed she hated him more whe he tried to show he cared..she just felt she didn't deserve to be loved!