Maybe part of the problem was that the scriptures he was reading were some of the most in-your-face scriptures in the entire Bible that really point to Jesus being the only way of salvation in the Bible. Maybe John 3:16 would have flown since many people have caloused hearts against that one. However scriptures like Romans 1 is not as well known to the secular public. In short - those were the perfects scriptures to use.
Answering Muslims: Christian Arrested in California for Reading the Bible in Public