Personally, I'm salty that Neji died. Pretty much what killed my interest in the series in the first place. Though I admit I'm saltier now that the manga ended...and I know he only died to turn his irrelevant cousin into a viable love interest.
As for the word itself...I don't know, it's better than "butt-hurt" IMO, given the alternate meanings. Though there's much worse internet slang out there.
But in this context...fans that cling to the ending because of their pairing and don't bother to analyze the obvious issues behind it really don't deserve your time. They're just sheep really.