Everybody, theists and atheists, have started to write the title of a book with lowercase letter b.
Why not Bible? Who has taught you to blaspheme the Holy Bible?
The order to blaspheme Bible must have original source. Is it Big Bang?
first of all, I don't think they mean anything by it -- it's just laziness, same reason I didn't capitalize the f at the beginning of this sentence.
I do suggest you develop a thicker skin. You are in a forum where not everyone accepts the bible as a divinely revealed text. some people have their own sacred texts, like the quran or the vedas or the book of mormon. Others have no religious text at all, either because their religion doesn't have one, or because they are not religious. you can't take it so personally when others do not adopt your religious text, if you are going to remain in a good mood in this forum.
btw, the default position is to consider any book just a book unless you have reason to treat it otherwise. it is not up to others to prove that the bible is only a book. It is, rather, incumbant upon you to prove that it is the word of God, same as Muslims with their quran, or hindus with their vedas.