It's not that you disagreed or wanted to discuss--it's that you left three comments full of very specific negativity and just had one very generalized sentence about how you liked the rest of the fic. In a thread where the atmosphere was supposed to be one of happiness, that just doesn't work. If you had left those three comments and then followed up with three comments of things that did work for you, I wouldn't have been bothered by the tone. But coming in and only saying negative things (including the bit about how it's totally not possible for anyone at all to find Spike unattractive, which is exactly the kind of universal statement that should never be used in a discussion of attractiveness because of the simple fact that attractiveness is entirely subjective) immediately put me on the defensive and made me feel like you were picking on me. I have people disagree with me all the time in my journal, but they usually try to do it in a way that shows that they're trying to look at things from my perpsective (which is something I always try to do in return) and in a generally positive tone. I also steel myself for disagreement when I post a discussion post in ways that I definitely do not for fanfic. The general fic protocol that I've found across all the fandoms I've participated in (and there are a lot) is that if your overall comments skew towards the negative, you just don't review unless someone specifically asks for concrit. Otherwise, you can leave some criticisms, but only if you're going to balance them out with positive things as well. That's the assumptions I (and, I believe from my interactions throughout fandom, most people) make, so when someone doesn't follow those unwritten rules, I'm totally not prepared for it.

It is, of course, entirely your right to disagree with anything and everything I say. But I always try to keep my journal a place of positivity (there's a reason I chose that Doctor Who-referencing quote for my title), so trying to comment from a place of positivity is something that I appreciate.