After running the BASH script for about 20 minutes, the following is a quick summary of my results:

192.34.76.2 ... 2 Fails
199.91.189.234 ... 2 Fails
206.126.236.19 ... 2 Fails
199.91.189.74 ... 6 Fails
216.221.156.110 ... 1 Fail
89.149.185.41 ... 1 Fail

ISP:RCN
Location: Newton, MA

Seems like 188.81.187.74 is the most faulty IP.