Why does the spamblacklist.txt get flagged as a virus or malicious file?

This file is a dictionary of "words" commonly found in comment spam.

It is used by our Human SPAM filter to identify a comment as likely being a spam comment.  It is taken directly from:
https://github.com/splorp/wordpress-comment-blacklist

If your web hosting provider is blocking this file or identifying it as spam, direct them to this FAQ resource as explanation.