I'm trying to understand the sevarah.
If the Tzedukim held that sodomy with another's man was NOT considered adultery, and a Shofet was toeh - by not reversing it to a Chiyuv it appears that there is agreement with the Tzedukim, when it's quite the opposite. So logic dictates that because the Tzedukim would disagree on a reversal you should reverse it.
Also the lashon written from the view point of the Tzedukim, wouldn't it make sense more to say on things that Tzedukim concur is the law with us etc.
Avrahom Kevelson , United States
Shalom Avraham,
Thank you for your question! I think the way you are reading, "Davar sheha'Tzedukim Modim Bo," in what I would call an overrated way. All it means is that since the Tzedukim did not accept anything that is not explicit in the Torah she'Bichsav, that is a good criterion to check whether the Dayan made a mistake or what he said is not even a mistake, because any schoolboy knows the answer. The example the Gemara gives is one of many, and it just illustrates a case by adultery that there is a Halachah that is not explicitly written in the Torah she'Bichsav, but is subject to no doubt by any Posek, and still this is considered a mistake because, bottom line, it is not written explicitly, and the proof is that the Tzedukim argue.
I hope this helps,
Aharon Steiner