Why Cristian's use the term father for God, Is it not a insulting ordinary word for God ?

We call God Father because Jesus told us to. That's the beauty of it. That's our relationship. We don't deserve to call God Father, and yet He treats us like His children. The Hebrew word is actually Abba, and a closer English translation is Daddy. We are all totally dependent on God for our very breath, and He loves us like a Father and provides for our needs like a Father. He is a Father to the fatherless, the people with no father figures in their lives.

Isaiah 9:6 For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace

Matthew 1:23 Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.

1 Timothy 3:16 And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory.

Ephesians 3:9 And to make all men see what is the fellowship of the mystery, which from the beginning of the world hath been hid in God, who created all things by Jesus Christ:

The relationship God has with his people is best described in human terms as being like that between a father and his children. Our God is not a distant God, He is a God who became a man and came to earth amongst us in order to show us what God is like. Now we have permission to call Him father. We are to respect and have a holy fear for Him, we know He will discipline us for our own good like a good father must, but we are 'adopted' into His family.

What word would be big enough for God?

No human language can fully express the One Christians call 'Daddy'

How small is your god that words are adequate?

If Jesus is God, will you explain this Bible verse?

"The Father is greater than I." - John 14:28

"But in vain do they worship me, teaching for doctrines the commandments of men." - Mark 7:7

"I do nothing of myself" - John 8:28

neither came I of myself, but he sent me. - John 8:42

"And behold one came and said to him, Good teacher, what good things shall I do that I may have eternal life? So he said, "Why do you call me good? No one is good but One, and that is God alone. But if you want to enter into eternal life, keep the commandments." - Matthew 19:16-17

"Hear, O Israel; The Lord OUR God is one Lord, and you shall worship Him with all your strength and all your might and all your soul and all your heart." - Mark 12:29

Jesus told us to address God as Father. I find nothing insulting in this terminology.

They use father in order to embrace the idea that he's a male, and that females were only made for man.

Sexism much?...

we can always call him the 'good shepherd .' after all that is what he is