The same concept applies here, as well. Pinchas, channeling the trait of Yosef haTzaddik (the gemara [Sota 43a] tells us that Pinchas' maternal grandfather was Yosef) was able to challenge and defeat the spiritual blemish that the sin with the Moabite women caused, thereby rectifying the aspect of kedusha, which was in peril. This is why it had to be Pinchas, why he had to risk his own safety in a true act of mesiras nefesh.
The rebbe concludes with an observation that is very pertinent to us, especially in this time of the year, with the Three Weeks upon us:
This is also the challenge of the generation of Ikvus d'Meshicha, in these two subjects (i.e. belief and holiness).
The closer we draw near to the final redemption and the great revelation of the Messiah, the Evil Inclination's power increases as well, in these matters. The rectification for this is through the aspects of Moshiach ben Yosef and Moshiach ben Dovid; Moshiach ben Yosef will first mend the blemishes of the Covenant (i.e. diminished holiness through immorality), and afterward Moshiach ben Dovid, who exemplifies the trait of Malchut, of Emunah, will arrive and mend the diminished emunah.
It is incumbent upon the Jew to learn from Pinchas, who was one man, and sacrificed himself for the sake of all Israel, for all of Israel is responsible for one another. Similarly, when a Jew strengthens himself in these matters, and withstands trial [of faith and holiness], he brings the salvation to Israel!May we all gird ourselves in preparation for battle; when we feel a sense of responsibility toward one another, and we wage battle shoulder to shoulder, we can bring Moshiach! I bless us all that this year we should merit to observe the Ninth of Av as the festive holy day that it is destined to be, when we stand on the solid foundations of belief and holiness!