If the ground premise is wrong, and you see where they are going with this silliness, it’s challenging on multiple levels to “let them finish”.
This will let you feel superior and get the pleasure of making the dumb person feel terrible, but it really won't accomplish anything productive. What do you hope to gain by doing this? Will they start being smarter? Will they be better at their job?
I'm sorry, doing what you describe is just being a bully. If management isn't dealing with the problem person you should privately make them aware of the issues (in writing if possible). If management is aware of the issues and won't do anything about it, well you did your part and you aren't allowed to fix the problem. Unless it is a life and death or national security situation, either accept that the dummy is going to be around or resign.
If they haven't done any work for a year their manager is useless. You work at a place where managers don't do their job. If you take it upon yourself to set this person straight, you are basically propping up this useless manager. Useless managers hire useless people and chase away good people. Fixing this problem treats the symptom and may let the bad manager last longer than they would have otherwise, which means you are going to have to go set two additional people straight about how useless they are next year.
I do not think it's bullying to give a bully a taste of their own medicine. It may not solve the problem, to be sure, but pushing back on bullies is not wrong. Pointing out their cognitive dissonance, and drawing a line from their stubbornness to being a bad developer is not wrong either. In particular where the manager doesn't care because 90% of the time that developer is delivering the goods, and just doesn't properly assess the ensuing (UI/UX) hostility.
Bad UI will piss off users. It's I completely expect they should express that frustration directly to the responsible developer. If that developer can't handle it, both accepting the criticism and making appropriate design adjustments, get out of the UI/UX development business.
I don't really subscribe to Kant-style categorical imperative thinking or defeatist attitudes, but in this case I've always made better progress changing an existing bad thing by being "demure" and accommodating. I might have agency to change things, but if an group of others have have agency to keep it the same, failing to cooperate is counterproductive unless I entirely opt-out or leave.
For milder/more moderate cases, giving someone a way to concede without publicly admitting they're wrong is a often a useful tactic to get said person to do things the right way while building trust in your relationship with them.
This is a management issue. In a rational engineering organization this guy's manager would be like "okay, so we know there's a problem with this tool. Now how do we work around the tool so we can move on to another problem?" And if the conversation becomes "workarounds are stupid we need to make them fix their tool" then the manager needs to be all like "I agree with you in a perfect world that's how things would work, but we're engineers being paid to solve people's problems and not to build the perfect software system. So build the workaround so we can solve the problem and we'll circle around and fix the tool when we have time."
It is failure of this one way more then just lack of pause - especially in long term relationships.
I think that an inability to admit a mistake is arrogant and results in a lack of accountability and ownership over individual's work. If someone makes a mistake they should be proactively owning it and trying to find solutions to avoid similar mistakes in the future.
> if you let people 'save face' they can just get on board and agree with you. If you force them to grapple with being wrong they will be difficult and will hate your guts
Your response to my post:
> I doubt you properly understand that other people are full thinking beings equal to yourself since you assume everyone secretly agrees with you about every detail of everything all the time and the only issue is whether they are going to admit it or lie.
To me, you're contradicting your own position. It also seems to me that you're the one that doesn't "properly understand that other people are full thinking beings equal to yourself" based on the arrogance and condescension of your response.
- let people finish their statement: If you don't let someone finish and you interrupt, they will decide that you are just refusing to hear them out rather than disagreeing. It doesn't matter if you can prove mathematically with extensive sources and footnotes, most of the time they won't be able to accept that you understood their point and showed it to be flawed.
- pause long enough after they speak: Again, if you instantly explain why they are wrong, most of the time other people will not be able to handle this. They will decide you didn't actually consider what they said. It doesn't matter what is actually true, and if you somehow do convince them that you are right they will be doubly resistant since you are making them feel stupid on top of everything else. A huge benefit of this and the previous bullet is that you will often find that at first you misinterpreted what the person was saying, so you were about to disagree for no reason.
- don't force them to admit to themselves that they were wrong: if you let people 'save face' they can just get on board and agree with you. If you force them to grapple with being wrong they will be difficult and will hate your guts. It may seem silly, but replying 'I don't think that will work because ...' is going to be the source of turmoil, when saying 'Interesting. Previously we did something similar to that but we had a problem where ...' is going to win the other person over instantly most of the time. Later they will see that they were wrong, but you didn't rub their nose in it and force them to grapple with it in a social setting where they are going to have to feel shame.
Failure to do these things is just what people mean whenever they say someone is arrogant.