"truth we all know but agree not to talk about"
Of course, since Wikipedia is the source this could all be urban legend but as always, when in doubt, we fall back on the Official Blog Policy.
The concept of "truth we all know but agree not to talk about" has both positive and negative aspects. On a personal and larger societal basis it can help keep the peace. It's hard enough holding relationships, communities and nations together - relentlessly picking at Truth can make it harder to coexist. It can also, when deployed on a large scale, make needed communication impossible, prevent the resolution of important issues and destroy the trust upon which relationships and societies rely. The trick is distinguishing between the two.