First of all, if you see a post that you think is rude, you can report it. I believe that it is contrary to the forum rules to behave rudely on this forum. Mods won't always respond to posts you report, but they will if they think something is in violation of forum rules.
Second, one of the rules of etiquette is that we are all required to give others the benefit of the doubt. That can play out in a lot of different ways, and people won't always agree on what specifically that means in every situation, but I think it's fair to say that if you think a post is too harsh...it's often better to assume the poster did not mean it that way and ignore it. Tone is difficult to communicate in writing, no matter how carefully you compose your thoughts.
Finally, to answer your question, I don't think that anyone ought to strive for more than civility and politeness on this board. I can quite vehemently disagree with someone while remaining perfectly polite. Civility is not always kind. Sometimes, kindness is less important than what a person feels they have to say.
And, to be perfectly honest, I talk to people on this board in much the same way that I would talk to them in real life. The only real difference is that I have time to compose my thoughts here, and I do not have that luxury in conversation. But, ironically, the fact that I have time to compose and edit my words here often means that I am less kind than I would be in real life. Because I have more time to think about what I'm saying, I am less likely to err on the side of kindness like I do in conversations where I can't choose my words as carefully.
I think it is important that we all treat each other with respect at all times, and that we all try to be as civil as we know how. But neither of those things translates to kindness in every situation, nor do I think anyone should have the expectation that it will.