VaYikra: Why "divrei kevushim" were needed for BN"Y to accept korbanos

"VaYikra el Moshe Leimor... " Rashi explains that Hashem told Moshe to speak to Bnei Yisrael with "divrei kevushim", words of supplication to win over their hearts. " Hashem speaks to me only because of you", Moshe told Bnei Yisrael. Moshe is told to respond to Hashem if Bnei Yisrael agree to accept these mitzvos of korbanos.
Why davka by the mitzvos of korbanos was Moshe told to preface the commands with "divrei kevushim"? And why do these mitzvos in particular require explicit acceptance by Bnei Yisrael?
If one is chotei b'mazid, the halacha is that through tshuvah m'ahavah the aveira can turn into a zechus. However, if one is chotei b'shogeg,the aveira even through tshuvah m'ahavah still obligates bringing a korban. How can that be true if shogeg is a lesser crime than mazid? The Imrei Elimelech explains that precisely because the crime is lesser, the deterrent must be stronger. A person who does a cheit b'mazid eventually realizes the enormity of the sin and returns to Hashem b'lev shaleim. A person who is chotei b'shogeg might tend to minimize the cheit as just a mistake - not so bad. Therefore, even after tshuvah, a korban is required.
The dor de'ah, the generation who received the Torah, was fully aware of the significance of shogeg as a cheit. They did not need the reminder of korbanos. Therefore, Hashem instructed Moshe to approach them with "divrei kevushim". Moshe was on even a higher madreiga than the dor de'ah and did not need Hashem's explicit "dibbur" for him to intuit the razton Hashem. "But", said Moshe to Bnei Yisrael, "For 40 years I listened to the "dibbur" of Hashem on your behalf, so you could listen in as well, even though this was beneath my madreiga. So too, I ask that even if it is below your madreiga, for the future doros who need it, accept upon yourselves the parsha of korbanos."