I often think I'm having a debate when I'm not. In High School, I took some speech and debate. In college, I had a few more courses. While not professional, I do have a bit of a knack for debating. While I don't now always remember the terms for all of the processes and procedures for a debate, I do understand what constitutes one and the general flow and requirements.
For example, a debate requires evidence or support. You can't just say whatever you want without supporting it somehow, with some sort of evidence. Debates also have limits. You cannot assert one thing, and then assert something else when the first thing is successfully argued by your opposition. In a debate, the one with the best argument, the strongest support, and the most consistent presentation is usually the winner.
However, the rules are different for an argument. In that, all of the above rules for a debate do not apply. A person who argues does not present evidence or support for what they say, typically. If they do, it is often cherry-picked and ignores anything that is contradictory. They do not stick to their main point and accede when it is proven wrong, they instead change the goal, add new limitations, or ignore whole swaths of what their opponent says. And, most arguers assume they have won when the other person just gives up in frustration or accedes that the goalposts have moved and widened so much that the person's argument has reached a point where it must be so generally correct that the other person cannot do anything but accede the point.
You see this a lot with "deniers." They do not, cannot, have a debate, because a debater with any evidence or support at all will crush them easily. Instead, they argue. They ignore data, they bring bad evidence (if any evidence at all), and they talk longer and louder until the person debating them just gives up and goes away. It is the rough equivalent of when children stick their fingers in their ears and say, "nah nah nah" until they get their way.
I have a few friends who argue instead of debate. And I usually get sucked into it either before I remember they don't understand how to debate or because it is a topic that I am passionate about. One person, in particular, uses the phrase "Yes, but..." a lot in his arguments because, frankly, I am usually able to point out the inconsistencies in his original argument fairly easily. When that happens, the goalposts move and they widen. If I don't recognize what is happening soon enough (and, shame on me, I often don't), the goalposts get so close and so wide that anyone can kick a field goal. Something he says must be true. When I accede that much, he generally ends the argument.
The frustrating thing is that, if the argument happens in public or on a public forum (say, via a group email), he and many of the others will think he won the argument, even though I have presented better, provided support, and kept to each topic as they came up. In a debate class, I would have won, hands down. But in the court of public opinion, I lose.
It gets frustrating.
My only recourse going forward is to try harder not to engage with these people. I need to recognize earlier that they are changing the topic, ignoring data and evidence, or speaking to hear themselves talk, and simply disengage from the discussion. I need to let my determination and natural doggedness go and walk away, even if it is a topic I'm passionate about.