Appreciating People

In Pirkei Avos (1:15) it says, "vehevai mikabel es kol haadom bisaiver panim yafos" -
"you should greet every person with a pleasant demeanor."
Why does the mishnah say haadom, instead of adom.
The same question could also be asked for the statement in Pirkei Avos (1:6) that says, "vehevai dan es kol haadom likaf zchus" - "and give every person the benefit of the doubt."
Why the extra letter "hey" before adom?? There must be a message here..

The Sfas Emes tells us that this little extra letter actually gives us the secret to having successful relationships. "Kol haadom" literally means all of the person. We learn from here that in order to be pleasant to every person and in order to judge them favorably we need to respect and appreciate all aspects of their being. Once we are able to recognize all of the great qualities in people it will be natural for us to greet them pleasantly and judge them favorably!

Let's take this even deeper. Rabbeinu Yonah asks a really interesting question: One of the fundamental concepts of Judaism is "veahavta l'raiacha kamocha" - "love you friend as yourself." Why is it that the word "raicha" is used here instead of a different word, like "chavercha?"
Rabbeinu Yonah says the most amazing idea which, if we really take to heart, can make our relationships much more meaningful.
He says that in the word "raicha" is the word "ra" meaning bad. What this means is that everyone has some bad in them, some type of flaw. We shouldn't even expect to meet perfect people, because people like that don't exist. Sometimes we see faults in people and from then on it's hard to think of them without thinking of their faults.
"Veahavta l'raiacha kamocha" is teaching us that in order to love people we need to look past their flaws and appreciate the greatness that's inside them.

(Step By Step, article by Rabbi Shalom Rosner)