This is rather old bug and not entirely correct. Current Parole version
0.8.1 in Testing and in Stable depends on gstreamer1.0*. Support for MP3
was never in plugins-good or in plugins-bad, it was in plugins-ugly. So
current version depends on gstreamer1.0-plugins-base &
gstreamer1.0-plugins-good, leaving gstreamer1.0-plugins-bad &
gstreamer1.0-plugins-ugly in the "suggests" section. Install what it
suggests to get MP3 support. Those plugins have this bad name for a reason,
and for the same reason they were not installed by default.
I vote for closing this bug as not relevant. Although I haven't checked
what's happening in Experimental with Parole version 0.9.2.