Absolutely not, on all counts.
I don't think anyone would "excuse" a character for attempted rape just because they like them as characters. Maybe a few of the fringe fans, but they're hardly reflective of the fandom as a whole. I admit that I'm a Spuffy shipper and a Spike fan, but that doesn't mean I'm blind to his faults or that I forgive and forget all of his sins. I'm sorry if I sound harsh in this post, but I find that accusation very offensive.
People have a hard time with this scene because it's a DIFFICULT scene. I personally think it was a huge error on the writer's part, but that's another story. As it happened in canon, it's the culmination of an incredibly complex and abusive relationship, and the circumstances surrounding the AR and the characters involved are very emotional and ARE ambiguous. While I do believe it's attempted rape, even the people who don't view it as rape in the traditional sense (ugh, and isn't it horrible that there's a "traditional sense"...) are not necessarily "making excuses". I don't see any rational person proclaiming that it's "okay" for Spike to have attacked Buffy.