Well, you asked why he might've cared so much, right? I will say though, it isn't my place to be any persons' mediator of peace, or a 'White Knight'. For that, I apologize, I don't mean to overstep any boundaries.
I just wanted to bring to light to those reading this thread that it might be wise, both on Smashboards, and in life in general, to make sure that a person could express their opinion in a way that isn't actively trying to make someone else feel worse. This may require us to go out of our way sometimes to make sure we aren't hurting others, but I'm sure it'll be beneficial in the long run. It may be beneficial to consider whether one's words, or even how they're "said" (on the internet, where there is no real sense of implications beneath words) could hurt someone else, before they're said.
I feel it's the first step in helping get rid of the toxins that exists between the divides in the Smash Community, any allusions (or illusions) of #OneUnit aside. Of course, how realistic this is, we'll only know if we try.
Now, I'm not saying that you were actively trying to rile anyone up, but I'm merely saying that it's probably that perception of your words as the reason why he reacted that way to your post, even though it may not have been the best way for him to react.
For future reference, I'm also not trying to anger you in anyway, and I sincerely hope I'm not, and if I am, I apologize.