Jamieson, Fausset and Brown on Revelation 2:15

15. thou--emphatic: "So THOU also hast," As Balak and the Moabites of old had Balaam and his followers literally, so hast thou also them that hold the same Balaamite or Nicolaitane doctrine spiritually or symbolically. Literal eating of idol-meats and fornication in Pergamos were accompanied by spiritual idolatry and fornication. So Trench explains. But I prefer taking it, "THOU also," as well as Ephesus ("in like manner" as Ephesus; see below the oldest reading), hast ... Nicolaitanes, with this important difference, Ephesus, as a Church, hates them and casts them out, but thou "hast them," namely, in the Church.

doctrine--teaching (see on Re 2:6): namely, to tempt God's people to idolatry.

which thing I hate--It is sin not to hate what God hates. The Ephesian Church (Re 2:6) had this point of superiority to Pergamos. But the three oldest manuscripts, and Vulgate and Syriac, read instead of "which I hate," "IN LIKE MANNER."