Red X means "disagree". That's it. Shouldn't make you feel too bad. None of us wants a forum where agreement is mandatory.
It is, in my opinion anyway, a snarky way to respond. You most likely would not be happy if I did this with this comment. It should be open for discussion. The OP of that thread, according to the people that I discussed this with, is not really known for playing nice. I also worked as a Mod for the old PopPhoto forums, which were quite popular at that time and I would never call someone out publicly before having a discussion with them privately first. And generally, would not call them out publicly anyway. There is a right way and a wrong way to go about this, and the OP was out of line and rude implying that I was lying. And as I said earlier, one disagreeable person does not a forum make. Block is a better choice if he didn't like my work. EVERY image I posted got called out. And being very honest here, I really don't give a rat's rump about his opinion.
Hmmm. I'm inclined to disagree, and instead suggest that an actual snarky remark is considered snarky, not a red "disagree" x underneath a post. If someone is upset over the way another member is speaking to them, I personally feel that is a valid concern worth addressing. If someone however is upset that another member is using the "disagree" function on their posts, I would be inclined to believe that the person leaving the "disagree" is not the issue, and instead see others reacting poorly to being disagreed with as the much bigger issue.
I have to agree with Zulu; no one should be subject to mandatory agreement. I personally think that finding better ways to handle the fact that someone isn't agreeing with another would be a healthier option for the entire community, rather than removing the function completely. The idea is uncomfortably close to needless artistic censorship, in my opinion.