Chukas HaAkum

As I said in the previous post, I have been in contact with Rabbi Broyde and he has given answers to some of my questions. However, as of now, I still do not have permission to reproduce the answers he has given me.
Based on what he wrote me, though, I will give an outline of the issues at hand. The first issue to deal with is the different shitos regarding Chukas haAkum, also known as Darchei HaEmori. This is the prohibition in the Torah that forbids us to engage in the practices of the non-Jews. An excellent article has been written on this topic by Rabbi Zvi Teichman in The Journal of Halacha and Contemporary Society (1981). This article is cited by Rabbi Broyde in his article, as well.
Boiling it down, there is basically a contradiction between the Gemara in Sanhedrin and the Gemara in Avodah Zarah as to what the "heter" for Darchei HaEmori is. The Gemara in Avodah Zarah seems to say that if the practice is non-idolatrous it is muttar. The language of the Gemara is that it is muttar if it is "an honorable rite". The Gemara in Sanhedrin, however, seems to say that the heter for Darchei HaEmori is that if the Torah says to do it, only then is it muttar in the face of Darchei HaEmori. Otherwise, it is forbidden.
The Rishonim take these gemaras in different directions. Here is a run-down of the shittos:

Shittas HaTosafos: If it is a practice for Avodah Zarah it is forbidden even if the Torah instructs us to do it. (Just like we don't bring sacrifices on Matzeivos because they began to be used for Avodah Zarah, even though in earlier times the Avos used Matzeivos.) If it is a non-idolatrous practice it is only muttar if the Torah instructed us to do it. This is obviously a very stringent shittah.

Shittas HaRan: If it is non-idolatrous, it is muttar. If it is idolatrous or possibly related to idolatry, it is muttar only if the Torah instructs us to do it. This is difficult in light of the Gemara in Sanhedrin that seemed to require the Torah's instruction even in non-idolatry related cases.

Shittas MaHarik: The MaHarik is a very similar shittah to the Ran, however, he elaborates more conditions. The ideas that the MaHarik states are also very similar to the Rema, and it seems clear that the Rema follows the MaHarik. Therefore, if we want to define normative halacha it would be good to investigate this shittah. The MaHarik holds that not only are idolatry related practices forbidden, but even practices with no logic to them at all, as well. The idea is that if we do something that has no reason to it, so we are only doing it because the non-Jews do it. That is part of the issur of Chukkos HaGoyim. Also, the MaHarik holds that any practice of non-Jews that departs from immodesty is also included in Chukkos HaGoyim. The Iggros Moshe in Yoreh Deah Chelek Daled Siman 12 deals with this shittah with regards to Thanksgiving. Rav Moshe in two different teshuvos seemed to contradict himself regarding celebrating and eating turkey on Thanksgiving. In one teshuva he implies it is a problem of Chukas HaAkum. In another, he implies it is only a chumra, but min hadin not a problem of Chukas HaAdum.
Rav Moshe says he is actually mesupek on the issue. The safek basically boils down to the following. On the one hand, we could say that all these practices on Thanksgiving have no real reason to them. As Rav Moshe says, "that which we find by many things that happen to people all the time and they are inyanim of tzaar and yet they are not in tzaar, and also inyanim of simcha that people aren't happy about, even at that exact time. And in this case [of Thanksgiving] they are happy and they made a set day for celebration and eating turkey for hundreds of years after this, that is considered something for no reason and is darchei haemori, because it is done for no reason or need, and therefore there exists the prohibition of U'b'chukosehem lo selechu......"
On the other hand, maybe even a small reason counts as a reason. As Rav Moshe says, "but [on the other hand] you could say that in order to avoid [the issur] we don't need such a reason that would [be good enough] for us to make a holiday if it happened to Jews. Rather, it is enough if the reason was enough for the non-Jews..."
Rav Moshe then seems to conclude in this teshuva that his opinion is really tending l'chumra based on the lashon of the Rema himself.
There are a lot of teshuvos from Rav Moshe on this and it is hard to pin down exactly what he holds. However, it does seem that Rav Moshe concludes consistently that, at the very least, a baal nefesh should be machmir. Rabbi Broyde deals with Rav Moshe's view quite a bit in his article. I suggest you take a look at the teshuvos yourself to see if you can determine how Rav Moshe really holds. My point is that even in the Rema himself it doesn't seem that pashut.

Shittas HaGra: The Gra first brings down the various shittos. He is then clearly bothered by the Shittas HaRan and MaHarik because they don't fit well with the Gemara in Sanhedrin. On this issue, he sides more with Tosafos. Then, at one point he seems to offer his own solution to the Gemaras. He says that when the Gemara in Sanhedrin says that the mattir of Darchei HaEmori is that the Torah instructs us to do it, it is actually lav davka. All the Gemara means is that if we are doing it for our own purposes as opposed to theirs, it is muttar. That is also what the Gemara in Avodah Zarah means. When the gemara says that since it is an "honorable rite" it is muttar, it just means that since we are doing it for our own reasons, it is muttar.

One of the issues I raised with Rabbi Broyde is that wouldn't it be advisable to be machmir like the Gra and Tosafos? Even if it is not the normative halacha, it still would be a worthy chumrah. From Rabbi Broyde's response (again I won't post the actual response until I have permission, here I am just posting the framework), I gathered that the issue really is do we follow the Gra and Tosafos in other aspects of our lives? For example, one may suggest that since we dress "like Americans" we are clearly not being machmir for the stringent views (unless you are chassidish). I would counter that this is not the case. There is a major difference between dress and celebrating Thanksgiving. Dressing in American style clothing would be muttar even according to the Gra. Rav Moshe in Yoreh Deah 1:81 says this explicitly. This is because by dress, the style can be regarded as equally Jewish as Gentile. It is not a type of dress that is specifically derived from the non-Jews. This view of Rav Moshe is brought by Rav Teichman as well. However, Thanksgiving is a holiday derived from the non-Jews. It may therefore be problematic within the shittos of the Gra and Tosafos.