"If a bird's nest happens to be before you on the road, on any tree or on the ground, young birds or eggs, and the 
One who fulfills G-d's commandments because he finds their "mercifulness" agreeable transforms HaShem's decrees into something dependent on man's approval.
mother is roosting on the young birds or the eggs, you shall not take the mother with the young. You shall surely send away the mother and take the young for yourself, so that it will be good for you and you will prolong your days." (Devarim 22:6-7)
It is learned from the statement "you will prolong your days" that adherence to this commandment will grant a person long life. In his Guide to the Perplexed (3:48), Rambam highlights the cruelty of slaughtering a mother with her young. Animals instinctively love their offspring and would suffer grief by seeing them killed or abducted. Ramban explains that this directive is meant to infuse compassion in people. He then makes a reference to the Talmud, which states, "If one says, 'Your mercy rests upon the bird's nest'... we silence him." (Brachot 33b) The Talmud comments, "It is because he attributes G-d's conduct to mercy when it consists only of decrees."
It is peculiar that our sages instruct us to silence a person for praising G-d. While the commandment to send away the mother bird obviously demonstrates HaShem's great mercy, the Talmud is teaching us a valuable lesson. One who fulfills G-d's commandments because he finds their "mercifulness" agreeable transforms HaShem's decrees into something dependent on man's approval. By such means, he attempts to cancel out the entire rationale for accepting the Torah.
Israel's Torah is not a man-made "religion," but rather the Divine Ideal for existence lowered into this world by the Master of the Universe. It is the blueprint and instruction manual on how Israel - as a holy national entity - must elevate mankind and bring G-d's Divine blessing to flow through Creation. Every mitzvah is like a faucet that when opened, sends Divine content into our world and elevates it to levels beyond where it previously existed. These faucets, however, must be connected to the correct plumbing in order for them to achieve their lofty function.
Each mitzvah must be performed in the proper time, place and appropriate situation. A person who performs the mitzvah of shaking a lulav on Chanukah does not bring any Divine content into the world. A lulav must be waved during the Sukkot festival. Shaking a lulav on Chanukah is similar to turning on a faucet with no pipe behind it. Nothing comes out. The physical act was completed, but not according to the Torah's instruction.
The same holds true for a Jew who observes mitzvot outside of Eretz Yisrael. He is performing the actions, but he is not enhancing Creation on any spiritual plane. There are no pipes behind his actions because the mitzvot are meant to be fulfilled in a specific geographic location. This is why so many of history's great Torah luminaries describe mitzvot outside the Land of Israel as mere practice (to guarantee that Israel not forget them during the exile). The full expression of HaShem's commandments is only realized when performed inside the Land of Israel, as nearly the entire Book of Devarim instructs.
What would an egoistic person do when confronted with the commandment of packing up his life and moving to Eretz Yisrael?
An important function of HaShem's mitzvot is that they work to fetter man's ego. If today a Jew fulfills a decree because he intellectually agrees with it, there is a danger that he might reject a mitzvah tomorrow if he finds it difficult to understand. If he is used to performing mitzvot only because he finds them morally acceptable, then he might reject a Torah commandment if that particular commandment contradicts his personal sense of morality. While mitzvot like charity, mercy to animals and respecting one's parents might be agreeable to most people today, what would an egoistic person do when confronted with the commandment of packing up his life and moving to Eretz Yisrael? What about mizvot that involve physically harming Israel's enemies or destroying churches in our homeland? Will a person be able to fulfill such decrees if he finds them offensive or difficult to understand?
It was for this reason that our sages instruct us to silence a person who praises the mercy of G-d's Torah. The mitzvot are not dependent on man's personal approval and they do not need the endorsement of modern civilizations. Israel must do what is right from a love of G-d and an understanding that His decrees are eternally correct. Israel must pursue peace and justice by virtuously accepting the yoke of the Torah and submitting all personal considerations to HaShem's Divine Will. And through this submission, we should merit complete Redemption and the full expression of G-d's Name in this world through the glory of His Kingdom from the Nile to the Euphrates.