Are you saying you choose to respond because you are stubborn? We all have our reasons for making the decisions we make, but, in the end, it is us who makes the choice.
In this case, you are correct. After all, I could have just as easily made the choice not to respond to a cheap gimmick thread, and that was equally as tempting as responding. However, free will is not binary, either there or not there. If that were the case, addictions, habits, etc. would not exist. Free will is, in fact, a SKILL, and must be cultivated in order to be strong.
Let me give you an example: if we all make our own choices totally because we choose to, I should have no problem doing my work, right? Guess what? Last time I tried to do very simple and easy homework, I got what amounts to a panic attack and just froze and went braindead (probably not literally, but I just sat there with nothing going on in my head and not moving) for about fifteen minutes, and even after that it was impossible for me to focus on anything brain-engaging for the rest of the day. I had absolutely NO control over that. Sure, I had the will to at least try, but not the will to stand up to the EXTREME desire to not do it.
But this was months ago, and I've since learned a method for strengthening willpower, and since then it's been a lot easier for me to "just do" other duties. I haven't had a chance to test it out on homework, yet, as I've been taking this summer off, but in about a month, when school starts back up, we'll see how much progress I've made.