Jaqen, I am sorry that you have encountered this person, but at least you have found out what he/she is like straight away.
Folks here regularly jumped in to help our dear OristarA for years, as he/she asked question after question.
Virtually every question of his/hers was answered, and over time we saw him/her develop and improve, until suddenly the politeness stopped and the nasty, argumentative arrogance took its place.
To me, OristarA clearly showed his/her self as a classic troll. What we had done here, was to teach a troll how to troll effectively in English.
We had been duped.
It all came to a head a week or so ago, when folks here seemingly had enough of this nasty ingrate, and took him/her to task.
Now, very few people have time for him/her, and personally, I have the troll on ignore.
By responding to the troll, you are being lured in to do battle. The very best thing to do is to put the troll on 'ignore', then they disappear from view.
The troll will try very hard to goad you into further argument, but I advise you strongly to just let any insult pass and totally ignore it.
Hopefully, one day, the troll in question will get fed up of being ignored here, and move on to pastures new.
A very belated welcome to able2know, by the way.