Post Script: I quoted the Sha’arei Teshuvah not to prove Chanufah (flattery) causes Chillul Hashem (which is a Gemara), but to show when it applies and when not.
And if one’s life is in danger, obviously one may not be honest, or even merely silent. Some other important points are summarized by Orchos Tzaddikim “Sha’ar Hachanifus”.