"can't underestimate"

[sagehen]

Listening to a discussion of the Hoosier/Terrapin game ths morning on NPR
reminded me once again of a frequently-heard oddity of current speech,
somewhat akin to the "could care less" trope.  In speaking of the high
level of determination of the Maryland players, speaker says: "you can't
underestimate the determination".... while really meaning "it would be hard
to *overstate* their &c."  This occurs in constructions with both under-
and over- estimate and state in all  permutations, very often turning the
intended meaning on its head.    I suppose it's the quasi-double negative
that gives rise to the confusion.  It differs from "could care less," I
think, in that the latter is more or less conscious, whereas I suspect that
this one is  simple confusion.
A. Murie