It is true that anyone can prove almost anything out of the Bible if:
1. The Bible is taken out of context
2. The Bible is interpreted figuratively instead of literally.
You see, Bible interpretation requires rules like everything else in life. A football game without rules would be a disaster, and so is Bible interpretation done according to whatever anyone thinks is right.
Figurative interpretation leads a person to come to the conclusion that whatever he or she believes a verse in the Bible means is what it means. Literal interpretation means that the Bible means what it says and says what it means.
For instance, John 3:16 says, "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life." What does that mean? It means just what it says. God loved the world. He demonstrated that love by giving His Son, Jesus Christ, to die for the sins of the world on the cross. Whoever believes in (trusts in, relies on) Jesus Christ will not perish in Hell but have everlasting life with God.
Of course, there is figurative language in the Bible. For instance, the Bible says, “The voice said, Cry. And he said, What shall I cry? All flesh is grass, and all the goodliness thereof is as the flower of the field:” (Isaiah 40:6) This verse clearly says that "...all flesh is grass..." Now we know that our flesh is not made of grass. The writer is comparing flesh to grass. He is saying that flesh (life) is temporary like grass. It lives and then dies. This is a literary device known as a metaphor. God's word is filled with metaphors and similes. These are types of figurative language. They create vivid images in the mind of the reader. But it is clear from common sense when figurative language is being used and when it is not. The Bible should be read like any other book. It means what it says.
Also, verses are often quoted out of context to prove a point. For instance, did you know that the Bible teaches that there is no God? The Bible says, "...There is no God...." (Psalm 53:1) The problem is, the whole verse reads, "The fool hath said in his heart, There is no God. Corrupt are they, and have done abominable iniquity: there is none that doeth good.” (Psalms 53:1) By reading the entire verse, the verses surrounding the verse, and the entire chapter in which the verse is contained; and by interpreting the Bible literally, the Bible's meaning becomes clear.
So, it is possible to prove anything out of the Bible if a sloppy method of interpretation is used. If you want to know what the Bible really means, read it like any other work of literature and study it thoroughly before drawing any conclusions.