In the Hayom Yom of a few days ago, the Lubavitcher Rebbe writes,
The sins of Israel in the time of the Greeks were: Fraternizing with the Greeks, studying their culture, profaning Shabbat and Holy Days, eating t'reifa and neglecting Jewish tahara.
It is clear enough how most items on this list are sinful--"fraternizing" I could understand, on one end, as referring to eating meals or drinking wine with goyim, as we are not supposed to--but I'm really not sure what is technically wrong with "studying their culture." The only thing I can possibly imagine is that one shouldn't do that at the expense of Torah study unless there is some need. Is this what is being referred to here? Or is there something else sinful about studying Greek culture?