Mostly when people say "the Bible is not true" its usually a result of misunderstanding it (e.g. adopting Biblical literalism, not understanding the culture and context, not understanding nuance).
For example, you interpret Genesis as a story that makes a point and tell you something - it is like Jesus's parables (no one same says they are literal!). For example, that all human beings are made in the image of God - as we all look different that is clearly not literal. That we are all related and of one ancestry.
On the other hand you interpret the gospels as deliberately written biographies of Jesus. You interpret the epistles as letter written by their author to a particular person or group of people. You interpret the psalms as lyrics.
It is the traditional way of interpreting the Bible and few people had a problem with it until modern times.
However, much of the rest of the Bible should be read differently - the letters, biographies etc. Each document ("book") needs to be read appropriately and in context. Again, each can be compared to others in its genre, but its inclusion in "the Bible" (but there are lots of Biblical canons) gives it that extreme importance.
Sorry to nitpick, but there were quite a lot of "heathens" and "witches" who had faced some problems with the traditional interpretations of the Bible before modern times.