Paul Watzlawick said this quote

Our everyday, traditional ideas of reality are delusions which we spend substantial parts of our daily lives shoring up, even at the considerable risk of trying to force facts to fit our definition of reality instead of vice versa. And the most dangerous delusion of all is that there is only one reality.

~ Paul Watzlawick

...The world's benefactor has no choice; he is the surgeon who wields the healing scalpel. He does not want the violence, but the reality (which he has invented) drives him to use violence, in a way, against his will. Throwing a bomb into a crowded department store thus becomes an act of revolutionary love for mankind (and, in general, to quote Lübbe again, 'his primary intention is not to throw bombs into department stores or police stations, but rather into public consciousness.')

~ Paul Watzlawick

The ideological premise, however, can not be defective; it is sacrosanct. ... Whatever does not seem right, whatever does not fit, must be explained by something wrong outside of the ideology; for its perfection is beyond all doubt. In (t)his way the ideology immunizes itself by offering more and more hair-splitting accusations. Betrayal and the dark powers of inner and outer enemies lie in wait everywhere. Theories about conspiracies develop and conveniently hide the absurdity of the premise, necessitating and justifying bloody purges.

~ Paul Watzlawick

Radical constructivism, thus, is radical because it breaks with convention and develops a theory of knowledge in which knowledge does not reflect an 'objective' ontological reality.

~ Paul Watzlawick