I just finished talking to my neighbor who came over very distraught. He told me that he was driving into Jerusalem this morning when he saw a a Haredi man at Gilo junction, who was looking for a ride into town. My friend agreed and he got into the back seat. At 10AM the air was pierced by the siren. The driver stopped the car, got out and stood at attention, as is the custom. The trampist, however, demonstratively stayed seated in the car. My friend described to me how he grew increasingly angry as the two minutes passed. When the siren stopped he opened the backdoor and asked the hitchhiker to please leave his car. "I will not give a ride to someone who desecrates God's Name and the Memory of those murdered in the Shoah." "But our rabbis...." he started to protest. 'Don't know what they're talking about," he replied. The man got out and my friend went on his way.
Now, it seems, his conscience bothered him. Did he do the right thing? Was his indignation misplaced? He wanted to know if there was anything to the Haredi objection to the siren. (I always get asked this kind of question.)
As it happens, I wrote about this issue (Indirectly) in my doctorate and published it as an article. The bottom line is that there is absolutely no formal halakhic reason to object to standing for the siren. The prohibition against imitating non-Jews is confined to cases where a) the action has no clear, rational meaning b) it betokens arrogance and lack of modesty. If, however, it has clear redeeming purpose, it is allowed (Cf. Shulhan Arukh, Yoreh De'ah 178, 1). More to that, according to the source of Rema's ruling, (Resp. Mahari Colon no. 88) the operative concern is a desire to assimilate (להידמות להם). This clearly cannot apply to the siren because no other nation on earth has this specific practice. [For the purists, this satisfies the objection of the GRA (ibid.) based on Tosafos, Avodah Zara 11a.] QED
So why are the Haredim so vociferous about this? Why do they pound on the table so? I think its a delicate mixture of things. Among others, one might highlight: 1) It's an objection to setting up a separate day for Shoah commemoration, outside of Tisha B'Av, that contains ceremonies that are unprecedented in Jewish tradition. 2) It's an expression of rejection of Zionism and Israeli culture. 3) It's an gut reaction to the existentially grave questions of theodicy that the Holocaust raises specifically in the Haredi community, which bore the brunt of Hitler's (ימשו"ז) war against the Jews. (See Menachem Friedman's important study here.) 4) The prohibition against following בחוקות הגויים is a standard argument in pashkvillim against things that the community wishes to stop.
Did my distraught friend do the right thing? That's for him to decide (and God to judge). However, I did point out to him that Rabbi Lau (who is very careful not to offend the Yeshiva World) recently came out four-square in support of the moment of silence at the time of the צפירה. Even more to the point, there is a growing trend for Haredim to say Tehillim when the siren sounds. Some are quick to dismiss this. I, however, think it's a very significant development. It testifies to the 'judaization' of this ritual, even by Haredi standards (and to the further Israelization of the Haredi community.) This is a very powerful, unifying move, which I hope will continue- at the side of other Haredi responses to the Nazis: Talmud Torah, Tefillah, Tzedaka, Hesed and large numbers of Jewish children (which everyone should imitate more).
The צפירה may well be a harbinger of the שופר גדול. In the meantime as I contemplate the חרבן, following the observation of R. Shmuel Sperber זצ"ל, the צפירה says to me that the only response I have is וידם אהרן.
כל בית ישראל יבכו את השריפה אשר שרף ד'.
ארץ אל תכסי דמם
וניקיתי דמם לא ניקתי וד' שוכן בציון,