Welcome back to "Doggerel," where I ramble on about words and phrases that are misused, abused, or just plain meaningless.
We've all seen a common troll reaction: In a long thread, filled with references, explanations, chains of logic, and so forth used to back up arguments. In my experience, such things exist almost exclusively in the skeptics' side of the argument, but I digress. Eventually one troll gets sick of arguing over the facts and simply says, "that's just my opinion."
This is, of course, usually an effort to stop all debate, as if you should treat opinions as sacred and beyond questioning. Of course, there's also the difference between a conclusion arrived at through evidence and reasoning and opinion, though the media's done a fair job of covering up that distinction. If you're talking about science, you'll have to deal with the evidence.
You can believe what you want, but that doesn't take away our right to convince people otherwise. If you aren't willing to change your mind when given evidence, and don't want to be criticized for having an opinion, it's probably best that you don't express it among people who will take you to task for it. That's just a suggestion, of course.