I came here to point out that the term "brutalism" is abused horribly (as is "modernist", although when it comes to boingboing, neither can compare with the routine Geneva-convention-busting treatment of "minimalist").
A good word to encompass both Breuer and these sandcastles would be "Bauhaus". If "brutalism" has any meaning at all, it doesn't apply to these sandcastles, and is tenuously connected to Breuer.
The term doesn't stem from "brutality" in the sense of beating you up, but rather from the French sense of the word brut, as in raw and undisguised. Brutalist architecture is executed with straightforward, decisive processes (especially in-situ concrete) and wears the nature of its construction and materials openly. It doesn't dress itself up like classical or vernacular styles, nor does it take the contrivedly minimal forms of other schools of modernism.
ETA: DGMW, I like the sandcastles