Sitting at the gate of Sedom, Lot notices two strangers and invites them in. Despite his apparently good intentions, the townspeople are ready to pounce on him, as well as his guests. That does not surprise us for, after all, this was Sedom. What does surprise us is that Chazal pounce on Lot as well, criticizing his Chesed as not being up to the standards of his uncle Avraham. (See, for example, Rashi's comment on יט:ב ד"ה ולינו ורחצו רגליכם). To be perfectly honest, isn't it a bit unfair to hold Lot up to the standard set by the master of Chesed (and probably never matched by anyone else)?
A look at one aspect of Lot's life reveals some interesting insight into his development. After being raised in Avraham's house, Lot decides that the time has come for him to venture out on his own, and his uncle opens to him all the options and choices of destinations. Lot chooses the fertile area to the south, near the (not yet Dead) Sea, and pitches his tents up to, but not into the town of Sedom, which is already known as an evil place (בראשית יג:יב). Apparently, Lot had absorbed enough in Avraham's house to know not to live in Sedom. Just one Perek later, however, we are told that Lot is living in Sedom itself (יב:יד), and by the time we reach our Parsha, he has achieved a position of prominence in the city. (See Rashi on ט:א, ד"ה ולוט יושב בשער סדם).
Lot is typical of the person who is affected by his environment, no matter what the environment may be. When in Avraham's house, he absorbed the values embodied by his uncle. Even upon moving toward Sedom, he tried staying on the outskirts of town to avoid being affected by them, but just being nearby affected him enough so that he was slowly drawn into Sedom society. It was in that society that he met his wife and raised his daughters (and we know what his daughters were like).
Despite becoming an integral part of Sedom culture, Lot still retained some of the values he learned in his uncle's house, although they may have been affected by his stay in Sedom. It is no accident that our Parsha begins with the story of the three guests invited into Avraham's tent, and continues with the story of Lot's guests. Even the language used in both incidents is strikingly similar. Yet the critical thing to notice is not only how similar they are, but also how different they are. For example, Avraham is described as looking for guests (וישא עיניו וירא) whereas Lot sees his guests (וירא), but isn't necessarily looking for them. Another example: Avraham runs to greet his guests (וירץ), an action conspicuously missing from Lot.
Another key difference in the two acts of Hachnasas Orchim is the role played by the respective families in those acts of hospitality. Avraham gets every member of his extended family involved in the act - Sarah bakes the Matzohs, the lad cooks the meat, and Avraham serves the meal. (This may be what the Torah is referring to when Hashem says about Avraham that his special relationship with Him hinges on the fact that he transmits his messages and values to his family members. See יח:יט). Lot, on the other hand, does everything himself. In fact, various Midrashim highlight the fact that Mrs. Lot was, at best, stingy with her guests or, at worst, responsible for secretly organizing the lynch mob that attacked them.
Growing up in Avraham's house, Lot had the opportunity to learn his uncle's values, and maybe even gain the strength to hold onto some semblance of them while living in Sedom. But what about his own children? How would they learn those values when their culture and environment was that of Sedom, not that of Avraham's open tent?
On the surface it looks like Lot is doing all the same actions that Avraham is - greeting weary travelers, inviting them in, feeding them, etc. In reality, however, all Lot was doing was aping the actions he witnessed in his uncle's home, but without internalizing the Middos and values underlying those wonderful actions. Lot was criticized not because he didn't meet the standards set by Avraham, but rather, because he merely copied his uncle's actions without understanding, appreciating or internalizing the values that sparked those actions. Avraham's kindness was inspired, and he was therefore able to inspire others. Lot's acts of kindness were mechanical - not only couldn't he inspire others, he couldn't even inspire himself.
Many of us have positive role models that we seek to emulate. Many of us do Mitzvos of various sorts. Let's make sure that we're not merely copying the actions of our role models or mechanically performing our Mitzvos, but that we're learning the values that inspire those actions, so that we ourselves can become inspired and pass that excitement on to others.