Ah, thank you, I wasn't able to find the actual study earlier. I'm not all that clever. On with the criticism!
Besides the fact that the music used is still mainstream within the broad spectrum of popularities that is extreme metal, the paper sums up my other concerns in the last half of page 5. When a person is aware that their answers are being isolated and observed among other answers in a study, they are sure to answer differently than if they they were not aware of being part of a study. This is a variable that can only be avoided if you have blind participants, which would surely be difficult to pull off when putting together a study like this, which requires voluntary cooperation of the participants. In other words; the participants may well have responded differently had they been unaware they were being studied.
The ultimate conclusion in this case is that attending a university doesn't help you overcome a shitty taste in music.
(In case anyone missed it, the bands include Enslaved, Cradle of Filth, As I Gay Dying, Disturbed, August Burns Red.)