I would be surprised if the purported Grothendieck quote is really his.  He does not lean to the short and sweet. It sounds more like an adaptation of another thing Deligne says in "Quelques idées maitresses de l'oeuvre de Grothendieck" (p. 13): "if the decision to let every commutative ring define a scheme gives standing to bizarre *schemes*, allowing it gives a *category of schemes* with nice properties."