And canon or no, it already happened and...
You're talking about the IDW nonsense? That was retconned out of existance/undone in 'Return To Sunnydale', there Spike tells Buffy that if he loses his soul she should kill him- so he's never lost his soul, not even for a little bit.
W&H still
tried- that means that they wanted him dark because he's considered a large enough threat to warrent those investments/schemes, not Angelus. Angel was just strong enough to hold onto his humanity through very trying times.
The rest...Angel's massive fault is that, because he obsesses with his past evils so much, he occassionally throws up hjis hands and looks for a 'quick fix' to his redemption- suicide by sunrise, going dark and warring with W&H, and Twilight- Whistler, the guy he trusted through all those years, gave him an 'out'. Guy's an idiot.
Just curious - what is Behaviourollogy? How does it show that Spike without a soul and a chip would revert back to being his demon-ness? And how is this different from Angel?
Part of behaviourology is
negative reenforcement- do this and get an electric shock/vomit inducing chemical/pain as punishment. (the opposite is positive reenforcement- Pavlov's dog, etc)
This basically what Spike's chip is- something deep in his cerebral cortex there to 'fix/contrl' his abberant behaviour with pain.
Ultimately behaviourology doesn't work (and was
proven not to work and is therefore mostly dismissed nowadays) for two reasons; firstly when the negative stimulus is removed then the patient always eventualy reverts back to their abberant psychosis- whether that is a phobia, a compulsion or whatever. This is what would happen to Spike
without a chip (the soul is of course a completely different thing), it might takes months but Spike would go back to kiling, he (the demon) would remember how much he enjoyed it.
The second reason is that the negative stimulus just creates a second set of aberrant behaviour to replace the first, a
new disorder, usually just as strong as the first.
For example a peadophile would be
cured of his desires but go on to exibit a violent hatred/crippling fear of children because of the pain the treatment had caused/contines to cause.
Spike fought to get his chip because he knew it was the right thing to do - why would he revert? He's kind of the clockwork vamp - he's been conditioned not to attack people - though soulless Spike did try to kill the girl you mentioned.
I presume you mean soul? Spike fought for his soul but he had the chip forced on him. Like I said, if Spike had had the chip removed at the end of S6 instead of getting a soul (and YES Spike did go on a quest to find a soul, I'm not one of
those people) then he would've, eventually, gone back to how he was.
....Unless, you
could argue that the chip was a success and that one set of behaviour (killing, murdering, violence) was replaced with another-
mania, which would explain why Spike fell in love with Buffy in the first place. He mind snapped because the chip was preventing his demon from acting out, so a new disorder was formed.
I'll have to think on that because I'm not sure if the theory works or not-
it would explain some things though.
If that was the case then Spike
would remain the way he was if he was unchipped but was without a soul- he would still love Buffy and help her the same as before.