Because it's not a correction. An important part of what I was trying to say in my actual comment is that one should consider that there might be nothing to correct. In my version, I've conveyed my initial reaction as a point of reference in case that's something they wish to avoid in the future, and then that I discovered I was wrong.

I suspect readings of it in a negative light are because of the context of the current conversation. Otherwise, I'm not sure how something that is essentially "at first I was confused and thought you were wrong, but then I found out I was the one that was wrong" is supposed to be taken negatively.