While I certainly agree with your sentiment the posting he was complaining about was far from being helpful. The first replying poster did not say he thought it was against code or anything else. He said he wasn't an electrician, didn't cite that he thought it was against code and just said that it looked like a fire waiting to happen. At the very least this reply should have said I believe it's against code and it looks dangerous. I do agree however that the OP was also in the wrong.
I would disagree with the statement that CDA's post was not helpful. Similarly, I to am not an electrician, but from my work with fire prevention officers and reading some of ICE's posts on this forum, I know that replacing what should be permanent wiring with an extension cord is inherently unsafe (a fire hazard). Working in a safety facing occupation, I too would express caution to anyone wanting to pursue this path for their project.
I feel the OP's response is more related to the fact that they were told what they already suspected (that the arrangement was inherently unsafe), but wanted to proceed regardless. In this situation, people engage in what we refer to as answer shopping. They either keep asking the same question in different ways or asking different people, until they get the answer they want. This way, they are not responsible for their own actions. They can easily blame others if something negative happens from the chosen course of action.
Additionally, when receiving CDA's response the OP likely experienced cognitive dissonance. Everyone believes they are a good person who does good things. Bad things they do get explained away as something anyone in their situation would do. It is important to understand that decision making happens in the emotional center of the brain, then heads to the logic center so we can justify the decision that we just made. There is significant proof of this where people who have suffered from damage to the emotional center of the brain cannot make even the simplest decisions like which restaurant to eat at. Creating a fire hazard is not something a good person would do, but CDA's post indicated that this would be the likely result of the proposed course of action. The OP then being confronted with this information, now experiences cognitive dissonance. This is when you have two competing messages in your brain simultaneously. Which will win? Well, there is plenty of research on that. The first thing someone hears on a particular topic will likely form the basis of their understanding on the topic. It does not need to be accompanied by any significant source of supporting documentation for most people. They simply accept new information as fact without any real evidence, formulating their position on the topic. Now to dislodge this position, it requires substantial supporting documentation, substantially more than it took to form the position initially (it's hard for people to admit they are wrong). Sometimes, the evidence requirements are so high, that someone may never actually accept they hold an incorrect position on a subject. The OP rejects the new information that they may be creating a fire hazard as a perceived personal attack (remember only a bad person would create a fire hazard). They respond in kind with an attack.
I have found the understanding of cognitive dissonance to be instrumental in how I deal with contractors and owners in my line of work. Ultimately, this information governs how I frame information to try and avoid cognitive dissonance where possible. You can do this a lot of ways, making them feel that they are not alone in their error of belief is a really easy one (people are a lot more comfortable being wrong if they are not alone). This also allows them to salvage their ego (another critical understanding in our work), helping to refocus on solving the issue instead of them needing to prove their competence to restore the damaged ego. I would suggest that the response from the OP is related to damage suffered to the ego as well.
Ultimately, I feel the response from the OP was inevitable, whether it was CDA or someone else since there appears to be a consensus that the arrangement is not in compliance with the code.