Amalek is described as "lo yarei Elokim" (yes, I know some meforshim explain this to apply to Bnei Yisrael). The Brisker Rav asks why this designation is applied only to Amalek -- were the other nations any less lacking in yiras Shamayim?
The Brisker Rav answers by quoting Chazal's explanation (Bava kamma 79, daf yomi learners take note) as to why a ganav pays keifel but not a gazlan. A ganav tries to avoid being caught; he steals at night, or hides in the shadows because he is afraid of the police. A gazlan will rob you in broad daylight without inhibition. Therefore, explains the gemara, the ganav is worse than a gazlan -- the ganav shows that his fear of man is superior to his fear of G-d, while the gazlan does not.
Couldn't one argue, says the Brisker Rav, that the ganav deserves to be treated less stringently, because at least he shows some fear, as opposed to the gazlan who lacks any inhibition?
The answer is, says the Brisker Rav, that the gazlan makes no cheshbonos at all and therefore follows whatever his desires dictate. He does not intentionally disregard G-d; G-d is simply not on his radar screen. The ganav, however, does make cheshbonos -- he is afraid of being caught and restrains himself accordingly. Once you start making cheshbonos, then the question begs itself as to why that restraint is shown only in the presence of man and not in the presence of G-d.
The nations of Canaan are like the gazlan who makes no cheshbonos. They would have attacked any nation that appeared threatening to them -- the Jewish people just happened to be the ones who were in their line of fire. Amalek, on the other hand, had a deliberate cheshbon -- "atah ayeif v'yageiah", they deliberately plotted their attack for when the Jewish people were least prepared to fight and saw battle as an effort to undermine the singularity of the Jews as G-d's chosen nation. The lack of yiras shamayis the pasuk refers to is not hefkeirus lack of ideology, but rather refers to a deliberate anti-religious ideology that ignores and undermines spiritual values.