Why are so many of the religious assholes?
General ignorance concerning God and the theology they profess to adhere to. Many haven't read the bible (if "Christian"). Many don't study the aspects of their faith. Many don't understand what it means to represent Christ or who Christ is. Many are simply nominal believers...they claim affiliation with a religion or denomination based soley upon scattered attendance at weekly services.
When questioned or challenged about their faith their ignorance quickly gets them cornered because they can't answer questions. In these moments they're often peppered with more questions (often accompanied by derisive facial expressions), they feel inadequate and frustrated (which they are in these situations) and their primary response is to lash out.
How do I know this with certainty? Because I used to be one of em.
1 Peter 3:15
15 Instead, you must worship Christ as Lord of your life. And if someone asks about your Christian hope, always be ready to explain it.