Judging historical people on today's social standards. . .

[Gene C]

Help. My daughter is writing a paper in her Music History class (she is a music therapy major) and has been given this topic: should we still listen to, perform, and appreciate music from classical composers who by today's standards were flawed individuals, who may have done/said/believed 'awful' things?

I don't know many individuals who are not flawed. We all are to some extent.
There would not be much music to listen to if we rejected the music from flawed individuals. Who gets to determine what flaws cause rejection?

If she has time, and hasn't already, the recent PBS special on country music tells about a few "flawed" individuals who wrote some very good music. Many suffered from addiction to drugs and alcohol. There are several "Christian songs" which talk about being caught up in sin (serious flaws). Amazing Grace comes to mind.
https://www.youtube.com/watch?v=NG0vH4WYChQ
The comments to the song are interesting, and may help your daughter with her paper, how the music and words from a flawed individual helped them.
Here is a 14 minute video, The Story Behind the Song
https://www.youtube.com/watch?v=8m8AHHduTM0

Good Luck