Why am I told specifically not to uncover my father's nakedness?

Question

I was flipping through Yevamos and saw that it said that the Torah does not explicitly state that one is prohibited from having relations with his daughter. I checked out the relevant passage in the Torah (Lev. 18) and found something odd.

All of the prohibitions of family relationships are phrased as "don't have relations with this woman," except for 18:7, which is the only one that prohibits a man.

You shall not uncover the nakedness of your father or the nakedness of your mother; she is your mother; you shall not uncover her nakedness.

If 18:22 prohibits homosexuality, why is the bit about the father necessary?
It can't be that it means to prohibit being with your father's wife, because that is already prohibited somewhere else (18:8).

Answer 1

To quote Rashi:

the nakedness of your father: This [refers to] your father’s wife. [But how do we know this?] Perhaps it is only to be interpreted literally [as an admonition against relations with one’s father, in addition to the general admonition against pederasty]. [The answer is:] It says here, “The nakedness of your father,” and it says further, “has uncovered his father’s nakedness” (Lev. 20:11). Just as in the latter verse, Scripture is speaking of his father’s wife [as that verse begins with, “And a man who cohabits with his father’s wife”], here, too, [Scripture is speaking of] his father’s wife. - [Sanh. 54a]

the nakedness of your father’s wife: [This admonition is repeated] to include [in the prohibition, one’s father’s wife, even] after the death [of one’s father]. — [Sanh. 54a]

In other words, either one alone would only imply while he is alive, or while they are married. The redundancy makes it more inclusive to state that it can never become permitted later.

Rashi is quoting how the Talmud analyses Rabbi Yehuda's opinion. The Sage's opinion in the Mishna is that it is, in fact, literally the father, and it comes to add a second prohibition - there are several Torah prohibitions that combine to be violated in a single act, so this would be another one of those.

Answer 2

A talmid of R' Noach Weinberg told me that R' Noach used to often say a pshat in that. The Torah is saying, even if you are going to stoop to homosexuality, but not your father. And the lesson is, just because you have stooped pretty low, don't throw everything away.