I have posted things several times that were misinterpeted, and I felt horrible, because how it was taken was not how I meant to say it (in fact, this very situation happened to me a few months ago). And, I have re-read some of my posts to see if it can, in fact, have been interpeted as being callous or rude. Sometimes, I have seen where it could have been worded better and had egg in my face, other times, it really couldn't worded any differently, and then there are the times that I clearly meant what I said...period.
I do take more time to review and read before I press the enter button, because it cannot be taken back. Or, I may try and further explain myself if there is a flame war based on a misunderstanding of how I worded something.
Maybe PM the person with a private explanation if this is really bothering you, or again, maybe just move on. This is an active site. We do move on past grievances most of the time.
As others have stated, it is REALLY hard to convey feelings at times on line because we see no facial expressions, we really do not know each other personally, leaving room to assume a lot. There are some people here whose posts I love to see, but I don't know anything about them other than what they post. I don't know if they take time to respond to things after thinking or that they are impulsive and rude.