I know a lot of arguments against the wearing Techelet from my research etc. and I would to now hear some arguments for the Techelet. Does anyone have any arguments that support the Techelet?
Numerous points were made here which need to be answered:
(1) Regarding the reasons we believe that the Murex trunculus is indeed the hillazon of hazal, please see my latest article: http://tekhelet.com/pdf/TekheletThreadsOfReason.pdf
(2) Regarding the Arizal's statement that after the hurban habayit tekhelet is no longer available, please see my article: http://tekhelet.com/pdf/HistoryMesorahNignaz.pdf
(3) Regarding the difference between Kela Ilan (Indigoferra tinctoria) and the Hillazon (the proposed Murex trunculus) - while the dyes today both produce the same color and are both fast to wool, in ancient times the dye processing most probably contributed to a difference in fastness; see http://tekhelet.com/pdf/testability.pdf
(4) Regarding chemicals, we use chemicals and indeed the Gemara itself says chemicals were used. For more on this, see: http://tekhelet.com/pdf/Sammanim1.pdf
(5) Regarding the Kinneret issue: Shlomo Moshe Scheinman (Solutions to Fundamental Problems Regarding Tekhelet) explains that the Kinerret is merely R. Yehuda's attempt to reconcile the fact that Zevulun, who is to be blessed with the hillazon, held that Zevulun’s territory did not get to the Mediterranean; but R. Acha in Zohar rejects this and holds that Zevulun did have Mediterranean access, so there is no need to postulate Kinneret.
One argument is from Chazal's silence regarding animal dyes. Chazal spend much time lambasting Kalei Ilan (the plant based indigo), but never once complain about a fake animal based indigo (by 'indigo' I mean a dye that is the right color and does not fade). So either there was only one animal based indigo dye and that was it, or there were others, but all were kosher at least Bedieved as Techelet. Either way, if we can prove that Chazal knew about an animal based indigo dye, it must be kosher for Techelet. As this article points out, people were using the Murex to dye BLUE (not just purple) even before the times of Chazal, based on certain archaeological findings. If so, it is kosher. And if we have it, we should wear it because God said so!
Based on overwhelming physical evidence. and
1) We knew the color from the authenticated remains of קלא אילן that were found in Wadi Murabaat, and Hazal say that the two are indistinguishable.
2) The massive archaeological evidence that Baruch Sterman came up with was convincing.
3) Rabbi Moshe Tendler had said that if there are physical remains of a tradition, then one can't say the Mesorah was lost.
4) Rav Aharon Lichtenstein paskened that if you put techelet on your Tallis, you should say שהחיינו with a ברכה the first time you do so. This find confirms the truth in Rabbi Tendler's statement.
As an aside, while Rav Hershel Schachter doesn't eat Turkey because there's no Masorah on it, he does have תכלת in his tallis
Normally, I would not want to give mystical oriented answers on this site, since they can be easily misunderstood, and it's a topic that normally should only be discussed in person. However, since it was implied in the comments that mystical reasons are an argument against techelet, I will explain the real reason of why I DO wear techelet.
It says that only in the times of Moshiach will Techelet be revealed again.
The story of the Murex being the correct animal has the following history.
Now, in the gemora in Sanhedrin, following a long list of statements about the age of Moshiach it says the following line (98a):
All the commentators say that this is the strongest proof for the times of Moshiach. The land will not produce fruit, but it will when the Jews come back to Israel.
Further (99a), Rav Shmuel says:
(this is the opinion cited by Rambam)
Also cited in many places, is the fact that the "Times of Moshiach" will happen "bit by bit", and according to the Rambam, will happen naturally over time. Further, as cited in Daniel, and Isiah, the prophecies regarding the return of the Jewish people to Israel will become clear to those in that generation, even if they are not clearly understood in previous generations.
In other words, in accordance with the words of the Kabbalists, Techelet has returned to the Jewish people in the times of Moshiach, as defined by R Abba. (with no dissenting opinion recorded in the Messora)
All of the above (Except for the history and timeline, that is my own personal observations) is inspired by and parts taken from the sefer "Torat Eretz Yisrael" by Harav David Samson, based on the statements of Harav Tzvi Yehuda HaCohen Kook. If any of this isn't clear, I suggest reading that book where many many more sources are brought down to explain these ideas.