Christians: Why do you "claim" the bible is the word of God when...?

It was written by Gospels [ People ] who had a different viewpoint on life at the time thus allowing for mixed and biased inserts into the bible, clearly this is the work of a man, an example of this is that back then, homosexuality was regarded as a sin [ still is ] and homosexuals were punished and persecuted. Now it is accepted amongst [ most ] society. Not trying to be mean but can you give me SOLID facts and justify it?