“One who mocks the dead is scorning his Maker” (Proverbs 17). The Gemora states that a person who comes within 4 cubits of a grave must hide his tzitzis lest he mock the dead, who cannot perform the mitzvah.
Now imagine that we are going to daven at the graves of the tzadikim. We are certainly free of any thoughts of scorning them. And yet our Sages ordered us to hide our tzitzis.
How much more so when we walk among the living, who are sensitive to every nuance of another’s behavior toward them, should we take care not to cause them any shame or embarrassment, for we would thereby be scorning their Maker. ~ R’ Nosson Zvi Finkel zt”l