I'm sorry but i'm a little lost as to the point you are trying to make. You can't really put forward that Spike is a different species and then use that to judge him by the laws of our species, which don't apply to him anyway.
My point is that because its inherently wrong for inter-species, its the 'residual' humanity within him that goes for the rape, and as its the human part that is doing it, thats why Spike can be held accountable, and why it IS attempted rape.
Like i stated, had it been him feeding then it was his Vampiric nature, but it wasn't, it was something fundementally wrong.
Vampires are a different species by nature. What exists inside is very different to human. But physically they are the same as when they were still alive. Just because they cannot (usually) have children does not change that they have all the right parts. Vampires still have the sexual urges they had as human beings, the difference is in how they feel about the person they have sex with.
That doesnt change the fact that Spike, who believes himself a man to an extent because thats how Buffy treated him, used that human side, those human emotions to attempt this act.
If we are going to go this route then you have to assume Buffy and Angel were wrong to have sex together (he was a vampire too, after all) and that Buffy was wrong to have sex with Spike in the first place. This takes us into a whole other debate.
I never ever defended Angel and Buffy or Spike and Buffy, because it IS wrong on a basic level...only difference...Consensual.
Again, all that still doesn't alter the main point of the argument, that Spike did not set out to rape Buffy simply because of the nature of what he was inside.
No, he didnt set out to, BUT at the point in the Bathroom, he made the decision thats what he wanted, and to hell with her pleads of no.
I'm sorry but there is no proof of that. Buffy got in a lucky kick and temporarily set him back but she was clearly wounded and, at the best of times, Spike was a match for her. It was obvious to anyone that if he had continued Buffy would have had a very hard time in defending herself.
There is no proof that this 'epiphany' you mention came at that moment either, infact we see a Furious Spike leaving.......we don't know at what point he makes the decision to search for his soul, just that it comes after.
What we do know for fact is that Spike ISNT a match physically for Buffy. The very nature of the Slayer is to be better then a Vampire.
And, again, you are talking about men, this is a discussion about a vampire. The men that supposedly believed the woman wanted are are either lying or sick in the head. A vampire, especially in the circumstances of the relationship he had with Buffy, cannot be judges using those criteria.
A Vampire whose boundries of Humanity/Vampire are so blurred, the creator of the show has stated his feelings are based in the human world due to him being abnormal.
Using the 'Spikes' a vampire argument only works IF he is simply a Vampire, with no obvious signs of emotional levels....BUT Spike shows these, he shows human tendancies, he shows human qualities......thus he is accountable for his 'human' acts. And attempted Rape, in this case, is a human act.