What sort of Chilul is the Pasuk now referring to?
Rashi: It is referring to feeding Terumah to Zarim. 1
Ramban #1: It is another warning against a Zar eating Kodesh. 2
Ramban #2: Based on the word "Yarimu", 3 it is a Lav against eating Tevel, together with the punishment of Misah bi'Yedei Shamayim.
Ramban, Moshav Zekenim (from Toras Kohanim): It is a Lav against a Zar anointing himself with Terumah 4 , or drinking it.
Targum Onkelos and Targum Yonasan: It refers to the Kohanim eating their Terumah b'Tum'ah.
Ramban: Because it wants to insert the punishment for the Kohanim who transgress (in Pasuk 16). And "Bnei Yisrael" is both the subject and the object ('The Bnei Yisrael should not desecrate the Kodshim of the Bnei Yisrael').
Moshav Zekenim citing R"Tz: This is a mere Asmachta that anointing is included in eating. It is mid'Rabanan, and Chachamim did not decree in a case of pain. One who has boils on his head may anoint normally without concern. Therefore, one may anoint with Chelev or a Tamei species if he has pain. If it is for pleasure it is forbidden mid'Rabanan, also for minors. If a wet-nurse anoints a baby with Isur, we need not protest, and even if she feeds him Isur, for Beis Din need not protest against a minor who eats Neveilos. See Ramban and R. Chavel's footnotes.
Why does the Torah write "Yarimu" (in the future)?
Ramban (citing Sanhedrin, 83a): It adds an additional Lav for eating Tevel, from which Terumah is going to be taken.
QUESTIONS ON RASHI
Rashi writes that the verse forbids feeding Terumah to Zarim. No such Lav is mentioned in the Gemara. Moreover, it is included in Lifnei Iver! And if so, we can explain "v'Hisi'u Osam Avon" simply; the Kohanim cause Yisrael to sin. We need not say that they bear their own sin (refer to 22:16:2:1) and the note there!
Gur Aryeh: Rashi did not explain like Targum Onkelos, (16) that the Kohanim eat Terumah b'Tum'ah, for the verse did not mention Tum'ah. Also, it should have said Kodsheihem, and not Kodshei Bnei Yisrael.
Refer to 22:15:1:2-4.