Loud music bothers me only during group rides, particularly guided nighttime group rides. It interferes with communication between ride leaders and their efforts to keep a large group safely together and herded through intersections.
I actually enjoy some of the music and I understand that some folks find the rhythm helps with their pacing and energy. But it's a distraction from safety efforts. They should use ear buds or turn down the volume.
But I don't want to be the curmudgeon so I don't say anything. It's really up to the group ride leaders.