Honestly, I'm not sure if that standard is absolute. I doubt a Crusader knight would be comfortable hacking off the head of a Muslim Jihadist in the presence of the Blessed Mother, yet no one on this forum would argue that the Crusades were evil.
You're misapplying the folk wisdom. These are two entirely different things. A soldier killing an enemy; or an executioner killing a heretic or a criminal, are examples of ugly, but necessary, duties. We do ugly but necessary things all the time that we wouldn't want to do in front of the Blessed Mother (certain bodily functions come to mind). Listening to music (or watching movies, or TV shows, or reading books) are things we do for recreation; for pleasure (pretty much the opposite of necessity). Therefore, the axiom is applicable to these kinds of things: Would you be comfortable watching / listening / reading it to the Blessed Virgin?
Actually, you'd be surprised. While most of the artists aren't Catholic, a lot of them are pretty much just indifferent to the Church, well, the successful ones at least, probably due to the fact that edgy anti-Christian rock and metal is terrible, and no one listens to it.
Firstly, one who is indifferent to the Church certainly cannot be considered a "friend" of the Church. Those who remain intransigently indifferent can, I think, certainly be counted among Her enemies.
Anti-Christian music in general - regardless of genre - is anything but unpopular. Some of the biggest and most "pioneering" artists of the rock genre (and its various sub-genres) have been fairly openly anti-Christian: The Beatles (despite what Roscoe would have you believe); The Rolling Stones; Pink Floyd; Led Zeppelin; Black Sabbath; Frank Zappa; Ministry; Metallica; Nine Inch Nails; Pantera; and Tool all spring immediately to mind.
Finally, what I was referring to in my original post was not so much the artists as those who push the genre - the agents, the record companies; the music media, etc. Those people are the primary engines behind the spread of the genre. Are they mostly from among the Church's friends or enemies? (Hint: Oy vey.)
Is the focus on melody and harmony that lifts the intellect and edifies the soul, or is the focus on the tribal rhythms, exciting little else than the lower passions?
I'm actually not that sure how to exactly tell which would be which.
That brings me back to a point made in my initial post:
It it objectively beautiful and harmonious,or objectively ugly, distorted and discordant (appealing only to badly-formed modern aesthetics)?
I know my aesthetics were badly formed by modern musical and artistic sensibilities. You quite a bit younger than me so it's apparent yours were too. Listen to more Sacral Music; chants, and polyphony. Listen to older, traditional music genres that formed in Catholic Cultures and you'll begin to discern the difference.
I was heavily into electronic music when I was young. By the time I was your age, I'd spent an inordinate amount of money on musical equipment and had begun a ten-year long period of making electronic music. The more I studied music - particularly older Western forms of music (which is to say, Catholic) - the more drawn to melody and harmony, and the less to brutal, primitive rhythm I became. Finally, this coincided with my re-conversion to the Faith, and my understanding of why modern rhythm-driven music was lower and less worthy than the music of the Traditional Catholic eras became more or less complete. That being said, my aesthetics were still badly formed, and so the music I used to listen to still appeals to that part of me - thankfully my better judgment prevails against that part.
Watch the video that + PG + linked to. It's excellent. Continue to immerse yourself in Traditional and Sacral music. Pray and Sacrifice. After that, Grace and Conscience will do their work.