Proponents of such acronyms encouraging new users to look the information up themselves are often discouraging questions that could easily be answered using the FAQs, Wiki or Google.
RTFM frequents questions that common sense should have precluded asking.
Some may choose to reply in this fashion rather than leaving the newbie without a response so as to clarify what types of questions are considered inappropriate, unintelligent or inconsiderate of others' time.
originally: "read the field manual" used by WWII soldiers when asked basic questions by new enlistees.
rtfm quickly spread to engineering, computer & technical fields, and has gained popularity with internet usage.
its applicability has increased dramatically with the advent of wiki, where the answer is already at everyone's fingertips.
rookie: how am i supposed to clean this m1?
veteran: read the field manual.
noob: how do i install linux?
1337: rtfm @ linux.org/docs/beginner/install.html
polite usage that will increase likelihood of a helpful response:
newbie: how do i...? i have already rtfm.