Clarification: And there is no punishment without a warning.

Implied Question: Then why does the Gemara at the end of the first Perek of Bava Basra that 'on that day' that Rasha (Eisav) committed five sins - 'he was intimate with a betrothed girl ... '?

Answer #1: The Gemara does not mean that they were all necessarily sins, but something disgusting.

Proof: For we see that it also lists that 'he despised the birthright, even though there is no La'av prohibiting it.

Answer #2 (Part 1): We also find later that the Torah speaks derogatorily about somebody who contravenes something that the Torah would later prohibit.

Answer #2 (Part 2): Such as later on this Amud, where the Gemara permits a Nochri to have relations with his daughter, yet the Gemara in Horayos (in connection with the episode of Lot and his daughters) comments that they, whose intentions were to perform a Mitzvah, were subject to the Pasuk "Tzadikim will go them (tha paths of Hash-m)", whereas he, who had in mind to sin, was subject to the Pasuk "and the sinners will stumble on them").

Observation: The Gemara could have answered that the author of the Beraisa is Tana de'bei Menasheh, who holds that every Misah that is mentioned in connection with B'nei No'ach is Chenek.

Explanation #1: Rashi explains that the Rabbanan include all Chayvei K'risus regarding the B'nei No'ach from "Ish Ish" with regard to whatever is written in the Parshah; whereas R. Meir does not Darshen "Ish Ish" to include.

Implied Question (Part 1): Even though earlier in the Sugya with regard to Birchas Hash-m, R. Meir did Darshen "Ish Ish", and the implication is that whoever Darshens one, Darshens them all ...

Implied Question (Part 2): On the basis of which we concluded above that a Nochri is sentenced to death on four of the Mitzvos B'nei No'ach.

Answer: There he (R. Meir) is expressing his own personal opinion, whereas here he is speaking according to R. Akiva, as the Gemara will shortly establish.

Explanation #2 (Part 1): However, when we included a Nochri in the Din of Arayos from "Ish Ish", that was with regard to Arayos that pertain specifically to a Yisrael; whereas the Arayos that pertain to them we learned from "Leimor".

Explanation #2 (Part 2): In that case, both R. Meir and the Rabbanan will Darshen "Ish Ish" with respect of Arayos that pertain specifically to a Yisrael, and it is the additional Arayos (pertaining to Nochrim as well) that the Rabbanan learn from "Leimor", with which R. Meir does not concur, because the Torah writes "al-Kein Ya'azov Ish", restricting them to Chayvei Misos only and no more (i.e. Chayvei Kerisos).

Explanation #1: Rashi explains that the Tana mentions this to preclude 'Horaso ve'Leidaso bi'Kedushah', because, since he is comparable to a full-fledged Yisrael, R. Meir decreed on him even with regard to his paternal relatives, even though those relatives were born whilst he was still a Nochri.

Explanation #2 (Part 1): One can also however, say the opposite: that since both the conception and the birth took place bi'Kedushah, he is like a Yisrael and is permitted even to his maternal sister who was already born before the conversion.

Explanation #2 (Part 2): Nor is it possible to decree 'that people may say we came from a more stringent religion to a more lenient one', since there is no basis to declare her Pasul, and they are certainly like a case of two different mothers.

Explanation #3: Yet a third possibility is that 'Horaso ve'Leidaso bi'Kedushah' has the same Din as Horaso she'Lo bi'Kedushah, ve'Leidaso bi'Kedushah'.

Question: Then why did the Tana not rather insert 'Horaso ve'Leidaso bi'Kedushah', to teach us a bigger Chidush?

Answer: Because it would be not be possible to categorically state that she has no paternal relative, seeing as, whoever is born to her father afterwards is Asur min ha'Torah.