Baha'is make it about the Baha'i Faith too, because, apparently, they teach that Isaiah 7:14 was a prophecy about the Messiah. Which, it seems incredibly obvious by the context, that verse 14 can't be separated from the rest of what's going on in chapter 7. Here's part of the
Jewish explanation...
God dispatched the prophet Isaiah and one of his sons to warn King Ahaz that the northern kingdom had formed an alliance with this King Rezin They had joined forces to “wage war against Jerusalem.” Isaiah tells King Ahaz (verse 4) that he should not be afraid because God will be with him and the invasion with fail. Additionally, within 65 years the northern kingdom will cease to exist and its 10 tribes would be led into exile by Assyria. This is where the idea of ten lost tribes originates.
Although Ahaz was an evil king, God would continue to protect Jerusalem in the merit of his righteous predecessors. When Ahaz ignores Isaiah’s warning the prophet tells him to request a sign from God. After Ahaz refuses this offer, Isaiah informs him that God will give him a sign despite his stubbornness. He tells King Ahaz that “The Lord Himself will give you a sign. Behold the Almah (הָעַלְמָה) shall conceive and give birth to a son and she shall call his name Immanuel.” Isaiah 7:14
The word Almah has been mistranslated by most Christians as “virgin.” In truth, this word means "young woman." Additionally, the definite article (Ha-ה) means "the" and indicates that the prophet is speaking about a specific woman who he can point to. Interestingly when Matthew quotes this passage he not only mistranslates “young woman” as “virgin” but, to deflect the reference from a specific woman standing before Isaiah, he intentionally mistranslates “the young woman” as “a virgin.”
The word “Almah” should always be translated as “a young woman.” This word alone does not teach us anything about her sexual status... "Betulah" means "a virgin who has not had physical relations with a man," regardless of her age. She could be 100 years old or 18 years old. If Isaiah had wanted to tell us the physical status of the woman he would have used the specific word “Betulah,” a word he was familiar with and uses in his writings (see Isaiah 47:1).
The sign mentioned in verse 14 to Ahaz is that the two kings who threatened King Ahaz would be destroyed quickly. This sign is described in the next verse: “before the child knows enough to refuse evil and choose good the land whose two kings you dread will be forsaken” Isaiah 7:15
Of course... that's their explanation, and it could be wrong. But it sounds better solid to me. But what do I know.