collectNWData needs root access in order to collect all necessary information. That's an important security issue and a lot of people don't trust scripts which are executed as root. That's why the script asks whether it should be executed as root. A negative response will cause the script to skip various analysis check.
Everybody feels uncomfortable when a script is executed as root which was created by a stranger. I also would feel very uncomfortable. You can trust me: The only purpose of this script is to collect network information, which unfortunately requires root authorization. There are no modifications done on your system. 
If you still have concerns just use Google and search for collectnwdata and you will find a lot of entries of people who sucessfully invoked the script and they got help.  No system was damaged.
Handling of sensitive data is described here in detail.
Starting with version it's possible to call the script as a normal user also .