(EDITED IN LIGHT OF COMMENTS BELOW)
I think that one of the things that makes math-SE so special is that mathematicians of many levels of experience are welcomed.
It's really important to me that we welcome people like Rajesh to our math-SE community, and unless a poster demonstrates clear "troll" behavior and will not change this behavior, we should work with them on an individual basis. I personally can understand his confusion, it reminds me of myself as an undergraduate; but this is clearly a poorly stated question. I think "What is X" or "where can I learn about X" is a standard novice type question, and in and of itself I do not believe this should be grounds for closing a question.
This question is not only about "what is X" questions, it's also about how to deal with a person who takes constructive criticism personally, and I think it's good for the community to close poorly stated questions and continue to give tough critical comments, these types of comments are more valuable for a student than trying to indulge their confusion, in my opinion.
I don't see any problem with a "what is X" question/a request for references, and I don't see that as the main issue which led to the contentious comments. The main problem that I see is that this question is overly broad, and should be divided into individual posts (for archiving purposes), and that he did not seem to do enough research on google/wiki.