In my opinion, using the argument that "a character is liked / hated [by any amount] so they should / shouldn't be in Smash" is fallible.
I always thought that we should be debating the integrity and possibilities of a character, rather than the interpretations of said character by "haters" and "fans". Besides, how can we truly say a character should be in Smash or not if we were to judge them simply on the amount or loudness of hate or love they receive? It makes little sense, and instead serves as a brooding ground for potential prejudice and backlash. Likes beget likewise.
At the same time, I am not demanding that "people should understand the full potential of characters before commenting", or such nonsense. Such a notion isn't even feasible, given that we all have other things to focus on in life.
What I am suggesting, however, is the idea of at least being open enough to talk about certain character possibilities as they appear in conversations instead of just shooting down such thoughts the moment they surface.
If we were to react in a way that is unwilling towards ideas or propositions (for example, possible characters in Smash and what the developers could do with them [i.e. Krystal]), we'd merely continue to encourage the possibility of incurring a "biting" response from those who are interested in said ideas or propositions.
What I'm really trying to say here is that you can potentially have a more interesting and enjoyable/enlightening conversation with someone willing to be open (regardless of their position) rather than someone who is either going to adamantly shove their ideas down your throat and/or someone who is not even going to consider other perspectives. Allowing oneself to be vulnerable to new ideas/perspectives is key, but that isn't to say you're required to make such perspectives a life-long study or something like that. It's all about being considerate "in that moment", as opposed to "having to absorb everything at all times".
Yes, this all includes the prospect of expressing concerns. That's what debate is about. "Flaming" or resorting to "easy negative arguments" (like the one discussed in the first paragraph) doesn't necessarily contribute towards debate in a positive manner, but expressing concerns with what could potentially happen does. There's a difference - which is mostly seen in sentence context and structure, word choice, or approach to the subject matter (this "difference" can be determined by observing the average responses by the other people in the conversation).
And as always, there's that third option of being a non-participant. If something is bothering you, remove yourself from the situation. If that means that you have to take time away from the computer, do it. It's not going to do much good to continue exposing yourself to something that's only going to end up giving you more stress than you need.
In the end, this isn't to say you should shoot yourself in the foot for having a knee-jerk reaction to something. If you have a negative reaction that is influenced by emotion like that, it's completely understandable. We're all human. Heck, some of you guys here know I've had my fair share of reacting strongly to certain things; I'm not going to deny it.
I suppose, then, that it would also be wise to not immediately react back to people who go about flaming or reacting to things so strongly - as there's really no need. As I said above, likes tend to beget likewise.
But I digress...
Adaptive Philosophy 101 with TheRandomCities4 or whatever...