Often used in short term, dangerous, is a way of insulting someone that what he/she has shown off is in fact his/her own ignorance and/or stupidity.
Person A: Light speed is already archived by humanity's technology five years ago. There're reports that show...
Person B: Sir, please don't try to be dangerous.
Person B: Sir, please don't try to be dangerous.
by iCarrot September 25, 2010