Golden calf was an assistant G-d?!

 Devarim Rabbah (01:02) R. Isaac said: When Israel made the Golden Calf, the Holy One, blessed be He, desired to destroy them, whereupon Moses said to Him: ‘Master of the Universe! This Calf will be of great help to Thee.’ God then asked him, ‘How can it help Me?’ Thereupon Moses replied: ‘Thou causest rain to fall, the Calf will produce dew; Thou bringest out the winds, the Calf will bring out lightnings.’ Said God to Moses: ' So you also are going astray after the Calf! ' Whereupon Moses exclaimed before God: ' Then," Why doth Thy wrath wax hot against Thy people" seeing that the Calf is nought?’ To Israel, however, he said: ' Ye have sinned a great sin.’ 

Bamidbar Rabbah (02:15) Moses’ plea: Lord, why doth Thy wrath wax hot against Thy people, etc. . Moses suggested: ‘This calf which Israel have made can now be of assistance to Thee.’ He can send down rain while Thou wilt produce the dew! ‘‘But,’ replied the Holy One, blessed be He, ‘is there any such hope from him?’ ‘Then,’ came Moses’ retort, ‘if there is no substance in him, why art Thou wroth? ' ‘Lord, why doth Thy wrath wax hot against Thy people... wherefore should the Egyptians speak... For evil did He bring them forth... Remember Abraham,’ etc. (ib.11 ff.). What follows in the text? And the Lord repented of the evil which He said He would do unto His people (ib. 14). ‘His people.’ Thus has been explained the text, ‘And it shall come to pass that, instead of that which was said to them,’ etc.

Shemos Rabbah (43:06) WHY, O LORD, DOTH THY WRATH WAX HOT AGAINST THY PEOPLE? R. Nehemiah said: When Israel committed that act, Moses arose to appease God and said: ‘Lord of the Universe! They have given Thee an assistant yet Thou art annoyed with them? Why, this Calf which they have made will be Thy assistant; Thou wilt cause the sun to rise while it will cause the moon to rise. Thou wilt look after the stars and it will see to the constellations; Thou wilt cause the dew to descend and it will cause the winds to blow; Thou wilt make the rains to come down, while it will be responsible for the growth of plants.’ Said the Holy One, blessed be He, to him: ' Moses, thou dost err as they do, for surely there is nothing real in it.’

Yalkut Shimoni (795)ד"א מהו אחרי, כביכול משה שהוכיח אותי אחר ישראל והוכיח לישראל אחרי. לישראל אמר אתם חטאתם חטאה גדולה. להקב"ה מר למה ה' יחרה אפך, מהו למה, אמר לפניו העגל הזה טוב הוא לך לסייע לך, אמר הקב"ה מה מסייע לי, א"ל משה אם אתה מוריד גשמים הו מוריד טללים, אתה מוצא את הרוחות והוא מוציא את הברקים, אמר לו משה הקב"ה אף אתה טועה בעגל, אמר משה רבש"ע א"כ למה ה' יחרה אפך בעמך, ולישראל אומר אתם חטאתם חטאה גדולה, משל למה הדבר דומה למלך שכעס על אשתו וטרדה והוציאה מביתו, כששמעו השושבינין הלכו אצל המלך ואמרו לו יאמרו כך אדם עושה לאשתו מה עשתה לך, והלכו אצלה ואמרו לה עד מתי את מכעסת אותו, קדמותך הוא תנינותך הוא. ד"א אלה הדברים ראויות היו התוכחות לומר על פי בלעם והברכות ע"פ משה, [אלא] אלו הוכיחן בלעם היו ישראל אומרים שונא מוכיחנו, ואלו ברכן משה היו אומות העולם אומרים אוהבם ברכם, אלא אמר הקב"ה יוכיחן משה שאוהבם ויברכם בלעם ששונאם כדי שיתבררו התוכחות והברכות ביד ישראל.

Tanchuma (Ki Tisa 22:2) Thereupon Moses stood before the Holy One, blessed be He, and asked: “Wherein am I guilty?” He replied: “Your people have dealt corruptly.” “My people,” Moses responded; “they are Your people and Your inheritance which You did redeem with Your own power. But what is their sin?” The Holy One, blessed be He, replied: “They exchanged their glory for the likeness of an ox that eateth.” Whereupon Moses said: “Master of the Universe, are You indeed jealous of an ox? Is he Your helper? Do You bring the winds while he causes the rain to fall? Do You make the sun shine, and he the moon to glow? Do You cause the trees to grow, and he the blossoms to sprout? After all, the ox is powerless; it merely eats grass and then is slaughtered. Lord, why doth Thy wrath wax against thy people? (Exod. 32:11).” He replied: “Is it honoring Me when they prostrate themselves before it and offer sacrifices to it? I have watched this people, and it is a stiff-necked people. Now therefore let Me alone, that My wrath may wax hot (ibid., vv. 9–10).” From this verse you may infer that the Holy One, blessed be He, is suggesting to Moses that he should plead for mercy in their behalf, since it is said: And I will make of thee a great nation (ibid., v. 10).

Ramban (Shemos 32:11) ETERNAL, WHY DOTH THY WRATH WAX HOT AGAINST THY PEOPLE? Now when Moses prayed about this great sin, it would have been fitting that he do so by way of confession and supplication, similar to what he said later on, Oh, this people have sinned a great sin, and just as Ezra prayed and confessed because of the faithlessness of them of the captivity, and there is no reason why he should say, why doth the Eternal etc.? Our Rabbis, prompted by this difficulty have in various homiletic ways tried to mention several reasons for Moses’ minimizing the sin before Him.

Berachos (32a) Moses spoke insolently towards heaven The school of R. Jannai learnt it from here: And Di-Zahab. What is ‘ And Di-Zahab’? They said in the school of R. Jannai: Thus spoke Moses before the Holy One, blessed be He: Sovereign of the Universe, the silver and gold which Thou didst shower on Israel until they said, Enough, that it was which led to their making the Calf.