I have absolutely had it with people who, when you make an ATTEMPT to have a meaningful discussion with them on an issue, pretty clearly have their own agenda and then lie and say that they don't have said agenda. I've seen it too many times on this forum to count alone (especially that one place that I wish I would stop posting in altogether because what I have to say, however much it's basically common sense at this point, deserves a bashing by somebody with a blatantly obvious and generally absurd agenda, political or otherwise). This type of garbage is intellectually insulting as well as completely and utterly uncivil.
This is intellectually insulting on the basis of a very well-known and generally true idiom: Actions speak louder than words. Indeed they do. A great example of such a thing on this topic is. Say, you think that people of all varieties should be treated the same, and you type out that opinion in a forum post. Then, somebody comments on it saying "well, these people don't because there's a bad apple among them." Of course, you, a reasonable person, make a post how that's a blatantly obvious logical fallacy in the form of a strawman (as it has nothing really logically backing it). Then they decide to totally backstep on what they just said, and then you call them out on that because of course they are lying for the sake of making themselves not seem anti-X (and also saying they aren't anti-X). But that idiom suggests (and anyone of sound mind can agree) that their earlier comments on the subject and the fact they even had to post them in response to something as well-meaning as what you posted are indicative of their TRUE feelings on the issue. In this specific example, the person you would be trying to debate with is clearly a bigot of some variety trying to hide behind a logical fallacy and words that mean quite literally nothing in context (Yes, this has happened to me. Actually, it's happened to me just like this example at least a couple of times).
This is uncivil because it makes it IMPOSSIBLE to debate with them and have an actual, meaningful discussion on the specific issue at hand. I mean the very act of them contradicting themselves so blatantly for the sake of making themselves look better is uncivil for obvious reasons. But the whole discussion is tarnished even not considering that. But then they'll act like you're trying to suppress them, which of course you aren't. You allowed them their turn to speak and you DID give them a platform, right? Well look where that got US! Anyways, it is tarnished because it clearly has no value to this kind of person in the first place. If it did, they wouldn't contradict themselves like this to try to go after you and make YOU sound bad because their agenda is more important than civility. Funny thing here is, most people like this will try to drag YOU through the mud and try to upset you to the point where your frustration starts to boil over for understandable reasons (and this can happen even if you have a good amount of self-control). I mean as I've stated previously the act of doing this is intellectually insulting, and depending on the issue at hand and how personal it is to you, it may also seriously hurt you on an emotional and even a personal level to see the $#!+ getting flung around. I mean seriously, if they try to personally attack you based on who you are (which depending on the topic, they might bring it up), it's obviously NOT a civil discussion! Even if they don't it's still uncivil to try to upset the person they're "trying" (NOT) to reason with nonetheless.
I'll also note why I put the political tag on this: 90+% of the time this happens, it's a political discussion, about a sensitive topic more likely than not. In that case, you can more often than not add "tribality" to the mix of reasons why this shouldn't happen. It's generally indicative of such a mindset, because generally tribal people will not betray the tenets of a very specific belief system, and this is how they attempt to accomplish that in this case by making a discussion, which they've normally tarnished even before this, completely and utterly uncivil to the point where the only actions to be made are either personal attacks or just walking away from the entire thing. Which of course they will say validates their belief system. Which it actually doesn't, and that should be pretty obvious! If they have to take a step such as this, it's clearly them that's in the wrong and obviously "losing" the argument. If they weren't, they wouldn't take this step in the first place to try to nuke the whole discussion. If they were "winning", it wouldn't be rational to do this in any way because this whole act is an act of desperation to try to make themselves look in the right here when they so obviously aren't, even in their own eyes. I note that they also must think they're wrong as well because if they didn't, well, they wouldn't try so lousily to correct themselves. Seriously, in doing this it makes it so obvious that they know they've totally screwed themselves before this to the point that anything else they claim to think here is utterly moot. So, now that I think about it, they must also be really stupid too!
I'll conclude on this note: this brand of nonsense doesn't belong ANYWHERE in any kind of "civil" discussion. It derails the discussion pretty much immediately, and it's indicative of a very closed-minded person that has no intention of actually listening to what you have to say. They act like this more often than not due to their tribalism telling them to do so, so they can attempt to salvage the argument. Well, we're laughing because new flash: IT ISN'T WORKING! I mean I've put four laugh emotes in this post because of how freaking funny it actually is that these, well, morons, do this. It's infuriating in such a way that it much less irks me than makes me feel like laughing, because of just how ridiculous it really is! However in all seriousness, this behavior is toxic and shouldn't be allowed anywhere near an actual debate. Unfortunately, this is the same internet where opinions are treated like facts and the other way around.