I'm thinking because they want to engage in debate and even friendly banter. Sometimes it can be a friendly conversation, even with a difference of opinion .. Sometimes, not so much .. Especially when one party refuses to use conversational etiquette and becomes belligerent and insulting. There is nowhere for a conversation to go but in the toilet, after that.
Why do some people ask questions on here and then want to argue with the answers they get in the comments? If you already knew the answer, then why ask?
Some people love to ask something and you tell them what they really prepared to hear and when you tell them otherwise they get wild!
But in another aspect, it depends how we define the "Argument" personally sometimes people that don't know me well, we talk and they think i'm arguing while i'm discussing, argument and discussion are different so! But because i have a high passion in discussion, people misunderstand me at first till they know me very well, and sometimes i ask something that i know the answer!
I just ask to see what others thinking about it and what's their perspective over it or guessing people's information and will open up a discussion with them. I ask some things on purpose to open up a discussion not because i don't know it! And i hope that's not what you considering as "arguing" in the comments!
My kids do this all the time to me. They ask and then argue. Once got into a big argument about the capital of Pennsylvania. It's Harrisburg, no matter how much a certain 12-year-old thinks it is Philadelphia.
Love of the argument maybe?
A couple of reasons, perhaps.
Some people are insecure and ask questions hoping that the answers given will support their point of view. If they get anything else, they argue.
Some -- like religious, or sometimes anti-religious posters -- will post a pseudo-question to use as a soap box and will take umbrage with any dissenters.
Some, and this would apply especially to the kids, will state something they've been taught -- either at home or at school -- and will assume that anybody who disagrees with them must be wrong.
Hey we could start drama Blurtit just for those people
They probably just want people to say that their answer is correct.
If them arguing back starts with "Surely..." or something like that they are probably just digging deeper to get more of a detailed answer.
I'm not sure I totally agree with the above answers.
There are two basic types of questions. The first is the type that have agreed upon factual answers or agreed upon methods to find answers in that genre. That includes a great deal of mathematics and what city is actually the state capital.
And even those may require explanations when the answers are counter-intuitive---e.g. If I am walking from the caboose to the engine on a moving train, I am moving faster than when I am walking on the ground beside the tracks; yet if I am also carrying a flashlight that is turned on, the speed of the light is the same whether I am on the moving train or standing motionless on the ground.
Then there are the questions that have widely differing answers even when the principles (e.g., those of logic) are agreed upon, but the assumptions from which we draw conclusions are not.
So a lot of the answers we get to such questions---the purpose of life, the existence (or not) of a god; socialism vs capitalism; etc., do not have an objective standard by which we may measure the "correctness" of the answer.
Thus the observation "...the intellect cannot be placed in possession of its object by an external agent that brings it there. " ("You can lead a horse to water, but you can't make him drink.")