An article at a site called “Torah Musings” analyzes blood donations from a Jewish perspective. The long article is a complicated discussion of whether blood donations might be prohibited because it benefits non-Jews. It is not always easy to follow such texts due to the religious terminology, but here are a few points to summarize it:

• The author begins by observing that “some have questioned the halachic [halacha = Jewish law] propriety of Jews donating blood”. This is, as we will learn, because it might help Gentiles.
• Jews donate blood because “Jews must participate in any life saving procedure with negligible risk in order to save a fellow Jew.”
• There is an obligation in Jewish law to actively save lives. However, the religious obligation to actively save lives refers only to other Jews. There is no obligation to save the lives of Gentiles. Indeed, saving the lives of Gentiles may actually be forbidden. For example, “Chazal [Talmudic sages] prohibited violating Shabbos [Sabbath] in order to save a non-Jewish life.” Also, non-Jews should according to the sages not be “saved from a pit into which they are thrown.”
• However, the sages realize that a refusal to save the life of a non-Jew may cause anti-Semitism and therefore harm Jews.  Thus, you may save the lives of Gentiles in order to keep Jews from harm (rather than saving them because you’re a decent person).
• The author notes that “one local rabbi recently suggested that there is a prohibition to donate blood to general blood banks (though he acknowledged that there is a mitzvah [religious commandment or good deed] to donate blood to Jewish causes).”
• The Talmud prohibits giving free gifts to non-Jews, the article continues, and donating blood to a general blood bank may be interpreted as giving something for free to a non-Jew.
• One sage suggests that it is not forbidden to give a free gift to a non-Jew if you know him, because then you might get something in return in the future: “when there is a reciprocal relationship one can rest assured that the generosity of giving a gift will be repaid by the Gentile in one way or another.” Giving to a Gentile without expecting something in return is not the Jewish way.
• The author says that “one of the primary claims of those who wish to prohibit donating blood to blood banks is that the majority of those who need the blood are Gentiles.” If the majority of receivers were Jewish, it might possibly be allowed.
• But the “rule of majority” is suspended in cases of life and death, and “therefore, even if one were to accept a prohibition to donate blood to a Gentile, the possibility that the blood may go to a Jew is sufficient to outweigh any such negative considerations.”
• Rabbi Menashe Klein argues that Jewish blood is sacred and may therefore not flow in the “impure veins of a Gentile.” He ”poetically refers to the blood of the [Jewish] person ‘crying out’ from the Gentile veins.”

Such is the hatred towards Gentiles in Judaism.

Some were upset that this subject was discussed publicly. “How can a post such as this not be fodder for those who feel that Judaism/ Pharisaism is an awful, misanthropic religion,” one commentator asked.

Another wrote that “since this is posted on internet it can become an easy source of antisemitism. One way to lessen finding via search engines is to put the most provocative material in Hebrew. . . . wish it never was posted.”

A third commentator was “shocked that R. Gil allowed this to be posted in a public forum. R. Lebowitz does not even bother with euphemisms which might not be so suscepible to a Google search. Any discussion of lo techanem [the Torah rule against doing anything good for non-Jews] should be conducted in a private forum.”

One comment admonishes another commentator: “do you feel uncomfortable with valuing the life of a Jew over a Gentile?”

Interestingly, there is a comment that apparently translates and quotes Rabbi Klein:

It is not proper to give Jewish blood – which bears the life, the soul, the spirit of G-d (as it is written ‘for the blood is the life’) and in [a] Jew, his blood and fat have been sanctified with the holiness of Israel – and transfer that it to the impure body of an idolater (Heaven forbid); the sound of his blood will cry out from the idolater, for it has been given over to an impure and defiling place.