Disclaimer:
"The patcher got flagged as a virus by my antivirus software! Is it a virus??"
-No.

"Then whyyy??"
-Generic detection. See below:
Here is a topic on F-Secure about what a Generic detection is: Generic Detection Description | F-Secure Labs
To put it in simple terms: Think of the Sentinels in X-Men: Days of Future Past, there are traces of genes that can produce mutated genes, so just kill them off to be safe.

The patcher can:
1. Request administrator privileges.
2. Download files from the internet.
3. Execute external scripts. (Apply/Restore)
4. Auto update itself.
5. Read/Write from/to the registry. (Read/Store settings)
6. Monitor other programs. (monitor NCGlobalLauncher/NCLauncher for new game updates)
7. It is also packed by a packer.
Get a better AV program.
P.S.: All the info above can be found in the instructions of the patcher itself.

"I don't believe you. Did you put a virus in the patcher randomly for no reason??"
-If you believe that the administrator of the Blade & Soul Dojo, who has been translating Taiwan single-handedly since January 2015 and has a pinned thread 45+ pages long, randomly decided to put a virus in the patcher, you have three options:

1. Don't use the patcher and figure out how to insert the translation yourself.
2. Get a better antivirus program.
3. Play in the original language.

Thanks.