WINE itself is open source, but it’s designed to facilitate the use of proprietary software. (This is because although it can be used to run open-source Windows software, best practice would be to recompile or port that stuff to Linux instead.)

If proprietary software is often malware and WINE is designed to facilitate proprietary software, then WINE is designed to facilitate malware.

(FWIW, I agree with the above statement, but use Wine anyway for a few games.)