We Jews have been accused of various heinous crimes throughout our long and tragic history. Perhaps, the most devastating accusation we have faced is the blood libel - murdering Christian children and then using their blood for baking Matzoh on Pesach. Of course, this vile accusation is absolutely ludicrous and false. The Torah warns us many times never to taste any blood. We are halachically obligated to soak and salt chicken and meat to ensure that all the blood is drawn out before we take a morsel into our mouths. We even check eggs for bloodspots to make sure that we don't ingest even a drop of blood.

Nevertheless, our enemies continue to make this base and vile accusation.
These charges have not ended since the time of medieval Europe. The Arab world has now adopted this canard from the Christians. There have been many books and dozens of newspaper articles published in the Arab press and media accusing Jews of murdering Arab children to use their blood. Recently, a series of articles have appeared in a Saudi Arabian newspaper with a new twist – Jews don't just use blood of Arab children on Pesach for Matzos but also use their blood on Purim for our hamantaschen.   

How did we become the subjects of such an absurd and horrible accusation that runs so contrary to our basic beliefs as Jews?  
Rav Elchanan Wasserman Zt"l explains this bizarre accusation with the concept of "Maaseh Avot Siman L'Banim" (The deeds of the Forefathers are a sign to the children). The traits and deeds, instilled into Am Yisrael by our forefathers, work both in the positive and negative sense. The Torah in Bereshit 37 tells us about the internal strife and hatred of Yosef and his  brothers. The Zohar explains that the Sinat Chinam that has plagued our nation since its inception, causing the Second Beis Hamikdosh to be destroyed, had its root in the hatred of the brother's behavior  toward Yosef.   

This is a frightening phenomenon.  Once the seeds of hatred were planted into the history of our nation by Yosef's slander of his brothers and their bitter revenge, it continues to affect us throughout the centuries. Thus, internal hatred is a problem that Jews will have to deal with until Moshiach comes.

Rav Elchanan Wasserman Zt"l takes this concept one step further. After the brothers sold Yosef, how did the brothers explain Yosef's disappearance to Yaakov? "They took Yosef's coat, slaughtered a goat and dipped the coat in the blood." (Bereshit 37:31) Then they showed Yosef's bloody coat to Yaakov, who then assumed that Yosef had been torn apart by a wild animal. By using blood to cover up their crime, says Rabbi Elchanan Wasserman Zt"l, the brothers sealed the fate of Am Yisrael.  Yosef's brothers use of blood to deceive their father has caused us to suffer from deceitful blood libels until this very day - Midah K'Neged Midah (measure for measure).