These people are engaging in the important mitzvah of Pidyon Shvuyim (the Redeeming of Captives). At a demonstration in New York City, they push for the release of thousands of Jews from the Soviet Union. Notice what it says on the kids signs. Where have you heard these words before?
Under Soviet rule, Jews werent allowed to practice their religion. They werent allowed to immigrate to Israel or America, and many Jewish leaders were put in jail. To help their Jewish brothers and sisters overseas, American Jews held demonstrations, petitioned the U.S. government to pressure the Soviets, and even smuggled Jewish books and religious objects into the USSR. By the end of the 1980s, internal changes and an economic collapse in the Soviet Union, along with pressure from the world Jewish community, changed the situation for the Soviet Jews and gave them new hope. Within a few years, hundreds of thousands of Jews were able to leave the former Soviet Union for Israel.
Sample Texts:
Do not stand idly by the blood of your neighbor.  Leviticus (Vayikra) 19:16
When the community is in trouble do not say, I will go home and eat and drink and all will be well with me.Rather, involve yourself in the communitys distress as was demonstrated by Moses (Exodus 27:12) In this way Moses said, Since Israel is in trouble, I will share their burden. Anyone who shares a communitys distress will be rewarded and will witness the communitys consolation.  Babylonian Talmud, Taanit 11a
There is no greater mitzvah than the redemption of captives. For a captive is among those who are hungry, thirsty, and unclothed, and he is in mortal peril. If someone pays no attention to his redemption, he violates the negative commandments: Do not harden your heart or close your hand (Deuteronomy 15:7), Do not stand by when the blood of your neighbor is in danger (Leviticus 19:16), and He shall not oppress him with exhausting work in your presence (Leviticus 25:53). And he has negated the observance of the positive commandments: You shall certainly open up your hand to him (Deuteronomy 15:8), And your brother shall live with you (Deuteronomy 19:18), Love your neighbor as yourself (Leviticus 19:18), Save those who are taken for death (Proverbs 24:11), and many other decrees of this nature. There is no mitzvah as great as the redemption of captives.  Rambam, Mishneh Torah, Hilchot Matnot Aniyim, 8:10