Or HaChaim on Numbers 14:16/אור החיים על במדבר י״ד:ט״ז

1 מבלתי יכלת, "due to an inability, etc." This may either mean that the people would believe that G'd never had such power or that He had lost such power due to old age, etc. (compare Psalms 14,1). Either way, Moses could not envisage a greater desecration of G'd's Holy Name than to allow people to arrive at such conclusions.

2העם, the people, etc. This verse is intended to counter G'd's intention to create a new nation from Moses' descendants. Moses argued that even this would be a desecration of the Lord's name. As long as G'd had not brought the nation to the land of Canaan His image would remain tarnished. Refer to what I have written on the word ושמעו on verse 13. The thrust of Moses' argument was that even though the Israelites had spurned their G'd, if He would retaliate by killing them in one fell swoop this would be a desecration of His name, world wide. When the Torah wrote in verse 13 "Moses spoke to G'd," the words "to G'd" may be a hint that his concern was for the damage killing the Israelites would do to G'd, i.e. to His image in the world.