In this week's portion, Behaalotecha, Moses tells God:
If this is how You are going to treat me, then, if I have found favor in Your eyes, kill me, and do not let me witness my evil. [Num. 11:15]
Sifrei Bamidbar 84:4 says that it really means "their" evil, i.e., the Israelites' evil, not Moses' evil, and that the inversion is just a euphemism, and that this is done frequently in the Tanach.
But in this particular case, why is Moses reluctant to talk directly about the people's sins? He wasn't before. For example, in Ex. 32:31 he tells God "‘Oh, this people have sinned a great sin!"