Criticizing tone instead of having rich discussion is a waste of time. In most cases, the time it takes to criticize tone and delivery can be spent arguing the issue at hand.
In a case where someone has the courage to raise their voice and question things publicly:
- Try not to discourage them from speaking up in the future
- Focus on what they said, not how they said it
- Address the issue in your response, always
In Paul Graham’s post about how to disagree, he states:
“So if the worst thing you can say about something is to criticize its tone, you’re not saying much. Is the author flippant, but correct? Better that than grave and wrong. And if the author is incorrect somewhere, say where.”
While it’s not constructive to react and submit knee-jerk comments, it’s just as counter-productive to criticize tone and delivery instead of offering solid reasoning as to why you disagree.
Of course, we can frame things initially in order to not invoke a predictable response to our snarky comments. But outside of insults or out-of-bounds comments (which are usually best ignored), I usually prefer to focus my energy on the problem, not examining words and etiquette.
Be wary of criticizing tone. It’s not as productive as it might feel and won’t do anything to change the end result.
morgamic 
I’d add that on the flip side, keeping things positive and not letting a discussion go negative is very important. However, once you start criticizing someone’s tone, the direction the overall tone of the conversation goes in is most likely negative and divergent from the main discussion. In all likelihood it becomes unproductive and risky to start picking apart how people say things unless they are way out of line.
And even then, if someone calls you a butthead in an otherwise good conversation replying to it is probably not worth your time and sinks you to their level. Be better.
This resonates with me as a tester. In my beginner days, I would look at a page and say to a developer, “that sucks.” While I still acknowledge gut reactions like that as important, I now understand that it’s just the beginning and that I need to dig into the why of “it sucks” to produce some real data about the suckage.
In relating this to the tone with which someone expresses their criticism, an irritated tone can be a valuable gut reaction, but it is important to get at the “why” of the reaction. These details often point towards more valuable information.
On the other hand, telling someone, “that was mean of you,” or dismissing someone’s strong reaction is its own personal insult and tosses out the chance of discussing the data behind the irritation.
I like the advice to “be better.” Although I may be human, I always try to set an example and am hopeful that others will do the same.