After the narrative of the spies and the subsequent outcry of the people in reaction to their negative report, Gd threatens to exterminate the nation. Moshe pleads with G-d to forgive them and invokes a curious argument. Moshe claims that the Egyptians will hear about this drastic action and they will say that the Canaanites will also hear about it, and rather than seeing this as a manifestation of G-d’s judgment they will attribute it to Gd’s inability to bring the people into the Land that He had sworn to give them.
Abarbanel finds numerous difficulties with this argument. First of all, why should G-d refrain from carrying out justice because of what the Egyptians would say? Secondly, having experienced G-d’s enormous power already, it is unlikely that they would attribute the punishment to G-d’s inability to bring them into the Land. Clearly, a military conquest of the Land would require less miraculous intervention than what the Egyptians had already experienced.
Abarbanel explains that even though the Egyptians experienced the enormity of G-d’s power in Egypt, they would say that it was limited to Egypt only, and could not manifest itself in Canaan. Since G-d did not have the ability to bring them into the Land, He had to find a pretext to eliminate them in the wilderness. Exterminating them would not be seen as a sign of Divine justice; rather it would be interpreted as a sign of Divine weakness. No earthly king would ever exterminate his entire people in the name of justice. This explains why Moshe emphasizes that the Egyptians will report to the Canaanites, to inform them that even though the entire region had heard of what happened to the Egyptians, G-d’s power was limited to them only.
Moshe was not advising G-d to overlook completely the transgression of the people. Rather, the punishment should be carried out in such a way that the Egyptians would not attribute it to any limitation of G-d’s abilities. G-d did not answer Moshe that the Egyptians would not see this as a sign of G-d’s weakness, but rather as an example of Divine punishment, because, having experienced first-hand G-d’s great love of the Jewish People, they could not imagine that the Israelities could ever transgress so egregiously that He would wipe them out in a moment. How could that happen to a nation for whom He had performed such miracles? The only explanation that would make sense to the Egyptians would be to think that there must be a limitation to G-d’s power.
Moshe’s plea to G-d, then, was to prevent this desecration of His Holy Name. Having heard what had happened during the Exodus from Egypt, the entire region was trembling before what they had seen as G-d’s limitless power. Moshe’s plea was an attempt to preserve this belief.