I'm sure we've all been insensitive at times.
Sensitivity is one of those aspects of life that you gain by receiving. If people were sensitive to you as a child, you likely gained great sensitivity. If you grew up with lots of insensitivity, you'll likely not a very sensitive person. Of course, like in most things in life, there's a continuum between insensitivity and sensitivity, and we all land somewhere on that continuum.
Insensitivity leaves a mark on all of us, and the only way to deal with that mark before it becomes a lasting wound is to get underneath it, understanding it, and channel the energy into something positive.
There comes points in our life when the insensitivity becomes too great and you simply have to remove yourself from that situation. That happened to me a few years ago in a situation--the insensitivity was extreme and began to affect my days. I had to make a break--it was the right thing to do.
In the best of circumstances, it is positive to stand up to insensitivity--to advocate for yourself or the insensitive situation at hand. Both at school and at home, I've experienced children doing that. I always welcome their honesty and advocacy, and typically apology and change my ways when insensitive. Of course, like most people, I want to be sensitive and strive for that.
We will all face insensitivity from time to time, and we will likely be insensitive at times too. That happens, but in general, it is best not to go down that road. Onward.