Did you ever consider using windows defender. Despite third party anti virus software, it is deeply integrated which keeps the introduced security holes to a minimum. After all, creating a trojan that is not being detected by any of the available anti virus solutions is not difficult at all. It just needs to be unique which can be achieved by encrypting it and anti virus applications introduce new security holes, since they need to intercept. (There are many viruses using anti virus application holes (there are more) instead of the system it self )
Antiviruses often have an option to exclude certain areas from scan and to temporarily disable scanning. I am not sure about Norton, but probably you can move the launcher to excluded folder and while downloading temporarily disable your antivirus. I personally recommend using Windows Defender, it works fine and is easy to use.
Wait.. someone actually installed Norton anything on their pc? Norton tends to be worse than the infection it is protecting you in my experience with it. There was a time when Norton products were half way decent, those days have long past.
Norton antivirus is literally the worst software of its kind. And instead of making it better, Norton pays other companies for installing it as crapware on peoples PCs. Use Windows Defender or Avast.
