Suppose I have some sort of Japanese language experience, though not really arrogance. The other night, on a poetry forum of all places, someone came across a comment I left somewhere, explaining something about Japanese (as it was sort of the topic), and I used a sentence as an example of how things don't necessarily translate black and white. Anyway, in this sentence example, which wasn't specifically addressed to anyone, I used だよ at the end of the sentence, and out of the blue someone commented that when discussing things with strangers I MUST use ですよ instead. I asked why and it turns out this person was a 25 year old girl from Japan. We ended up having a very short and limited text based dialouge, to which she concluded that my ability was 日本語上手ですね! Although it's not, but I understand the set phrase well enough to at least be glad she didn't say that she didn't understand what I was saying
Though, from a arrogance perspective, what I've found is not so much Japanese learners, but people whom take an interest in Japan (okay, in 少年アニメ; let's be honest) whom will use Japanese, a phrase, a name, etc., without really understanding what it means, and if you try to point out the error and give simple advice, they tend to get rather aggressive, as though their lack of knowledge is somehow not to be tested.
I don't really have a lot of experience with actual Japanese learners though. When it comes to those people they probably have far more experience with the language than I do so I'm probably paying more attention to certain patterns and phrases they employ; something new, as opposed to caring too much about their attitude.
But yeah, I honestly thought this thread as a joke topic. Wasn't aware such arrogance existed. Consider me coloured naive, lol