Minor Insult Overreaction

Troper A says something about Troper B. Troper B finds Troper A's saying to be mildly offensive towards them.

Troper B promptly flames the living hell out of Troper A.

Essentially, this applies when a character in a story finds something another character has stated or done to be far more offensive than it should have been, and acts according to their own judgement. May be used for Rule Of Funny, but is generally not very well-done.