Why are theists so hateful and vindictive towards non-theists?

I respectfully disagree. Theists trained in Eastern philosophies that pre-date the Abrahamic Faiths would never behave this way towards non-theists as Hinduism at most would consider a non-theist to have avidya or ignorance while allowing a non-theist the complete right to believe as he or she chooses to without shoving any deity down their throat and Buddhists would respect an atheist's point of view although Eastern Asian Buddhism is theistic unlike western Buddhism which is more philosophical. That is because there is a great degree of flexibility in Eastern religions -- you can worship anything you please or not worship at all as long as you focus on dharma or righteousness and karma or lawful and positive action. The Abrahamic Faiths do tend to hate atheists because they have been constructed on the "my way or the highway" platform and so are threatened by anyone who uses logic to tear them down. Eastern philosophies are built on knowledge or jnana and so welcome any kind of debate as a means towards gaining self awareness and enlightenment.