I don't presume to speak for Kilgore, but it seems to me that I have a moment of offense, quickly followed by an insight into what that's doing to me, and then the evaporation of the offense. The whole process takes just seconds, and sometimes it seems almost instantaneous. But maybe that's just me, and other people's mileage varies.
Quite similar, yes. In fact, this practice started years ago when I went through a period of having severe panic attacks. Basically, I learned to pay attention to the actual physical sensations and feelings which precipated a panic attack, which made me quickly be able to dissipate the attack before it kicked in.
I expanded this into paying attention to myself in all circumstances which caused an emotional reaction, not only in terms of physical sensations, but also in terms of what was the exact reason - inside of myself - for the feeling that was occurring. Quickly, you realize that most emotional reactions are actually a cooperative effort on your part - nobody can "make" you feel any way you don't want to, particularly when you understand your part in the reaction and what you're "getting" out of feeling that way.
I wonder whether it really is impossible to never be offended? From what little I've read of people like the Buddha (not just people as famous as the Buddha, but read of many lesser known individuals who were somewhat like him), it is indeed possible for some people to never be offended. And I'm fairly sure you don't even need to be "enlightened" for that to be the case with you.
I think it's like anything else. Any practice becomes easier and more effective the more you do it. Of course, this particular practice is impossible if one is starting with the mindset that their feelings are not under their control and are something that happens to them.
As for whether it's productive to react negatively to someone's comments, I think that goes without a doubt. But I don't believe one needs to take personal offense to come up with a negative criticism or a negative response to someone's comments.
The most productive, measured, and impactful criticisms I've seen were by people who took their own emotions out of the equation - even in a real world situation where insult/offense was directed at them. Some of the most admirable people I've known were the ones who learned to not only contextualize insult to not affect their emotions, but also utilize those situations to connect with the person committing the offense in a way which made them listen and respond, at least in the moment. When you take away someone's power to make you feel small, you can then see them as smaller and approach them from a position of power and influence.