Internet Flaming

Flaming is the hostile and insulting interaction between Internet users. Flaming usually occurs in the social context of a discussion board, Internet Relay Chat (IRC) or even through e-mail. An Internet user typically generates a flame response to other posts or users posting on a site, and is usually not constructive, does not clarify a discussion, and does not persuade others. Sometimes, flamers attempt to assert their authority, or establish a position of superiority over other users. Other times, a flamer is simply an individual who believes he or she carries the only valid opinion. This leads him or her to personally attack those who disagree. Occasionally, flamers wish to upset and offend other members of the forum, in which case they are trolls. Most often however, flames are angry or insulting messages transmitted by people who have strong feelings about a subject.

Some equate flaming with simply letting off steam, though the receiving party may be less than pleased. Similarly, a normal, non-flame message may have elements of a flame -- it may be hostile, for example -- but it is not a flame if its author seriously intends to advance the discussion. The word flaming is also sometimes used for long, intensive and heated discussions, even though insults do not occur.

Some forms of flaming can be attributed to deeper social or psychological weaknesses, probably from lack of exposure to a broader spectrum of disciplines that result in self-control issues.[3]
It is noted that Internet users are more likely to flame online than insult others in the real world, as the latter can lead to embarrassment and physical altercations, which online "anonymity" can avoid. Others urge against flaming, citing that people on the other side "have feelings too."

http://encyclopedia.thefreedictionary.com/Flaming+(Internet)