On a site like this, whenever you post something, be it an image, poem, journal such as this, you're inviting others to comment one way or another.
I posted something on someone's image that they shared. Nothing offensive or inappropriate, nothing insulting, just a simple comment, and the artist pretty much got pissed off about it.
Now, if I had said something negative or insulting, the person would have had a right. But what I posted didn't come anywhere near that level, and yet, she pretty much was offended, and got pissed off. Sad part is, it was concerning a place I know quite a bit about, and she doesn't.
If you don't want people posting replies or opinions, you've got 3 options: disable all comments on everything you post, don't post anything, or leave. Plain and simple.