"can't underestimate" = can't overestimate

[Jonathan Lighter]

A CNN analyst says "You can't underestimate" the Israelis' relief at
the release of Gilad Shalit.

I've heard this quasi-reversed construction frequently. It seems to
confuse "can't" and "shouldn't."

JL

--
"If the truth is half as bad as I think it is, you can't handle the truth."

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