Last fall, I wrote about a student who was disrespectful to the TA of my course. I decided not to intervene unless the problem persisted. It did not. In the post, I specifically wondered whether I wanted to know the name of the disrespectful student (the TA did not provide the name in our initial conversation). I was concerned in part because I found that I was assuming it was a particular student, and maybe that wasn't fair -- maybe I was assuming the wrong person.
In any case, I did learn the identity of the obnoxious student, it was the one I assumed it was, and I ended up very much enjoying having this student in my class.
He had a gruff way of speaking and could be very abrupt, and even seemingly rude. He was often anxious. He worked very hard, was not exactly a 'traditional' student in some ways, and he did not always deal well with his stress.
He was unambiguously rude to the TA early in the term, but once the course was underway, he found that he was very interested in the subject. He asked lots of good questions (including some curiosity-driven questions that were only tangentially related to the course topic), and I even got him to laugh a few times. When he figured something out, he helped some of the other students. I found that I liked him. I would be happy to have him take one of my courses again.
I think it is important to have these reminders from time to time that negative first impressions of students can change into positive impressions with more interaction. Just as we hope our students will keep an open mind about us as professors (and people) and appreciate our hard work, so, too, can we enjoy teaching students who seem like jerks (at first).