Bnei Yisrael were found guilty of creating an eigel hazahav at the precious moment of kabbalas haTorah and Moshe dares ask, "Lamah Hashem yechere apcha b'amecha asher hotzeisa m'Eretz Mitzrayim" , why Hashem are you angry at your nation that you took out of Egypt? How can one question "why" in this circumstance?! - such a blatant show of defiance justifiable should arouse Hashem's anger and dries out for punishment.
The Ramban suggests that Moshe's intent was to plead for the nation as a whole. True, a small group had sinned, particularly the eirev rav who Moshe himself had insisted be redeemed from Egypt, but the nation as a whole whom Hashem chose to redeem from bondage was not guilty.
I liked the Abarbanel's approach to the pasuk. Bnei Yisrael had been living in the surroundings of pagan idolotrous Egyptian society for 2 - 3 generations until Hashem took them out just a few short weeks before kabbalas haTorah. It takes more than a few weeks to undo the effects of years and years of cultural influence. Moshe pleaded to Hashem to not be angry at a people who just recently redeemed from Egypt, yet who were psychologically still very much under the Egyptian influence (compare with Ibn Ezra, Shmos 14:13 why BN"Y did not fight against a mere 600 chariots at Yam Suf).
I am tempted to rant, but am holding back - day l'chakima b'remiza that even if you are committed to the philosophy of Torah but are steeped in a culture that opposes that, you may be headed for trouble.