That's the important bit. You can choose an album, band, artiste, genre, song, anything music related and say you love or hate it but you HAVE to give a reasoned, coherent argument why you think that. Others are free to support or challenge your contentions, and you should try to engage them in mature debate, see perhaps if your view can be changed, should be changed, or if you, like me, are always right.
Seriously, it's not as simple as saying "Muse's latest album is crap" or "Genesis are rubbish" (shut up, Urban!)
or even "Free jazz is the best music in the world". You have to make a good case for your position.
I'm going to leave the floor for others for now, though as you'll no doubt be unsurprised to hear, I have some ideas of my own. However, no point in me leading every thread I make, so I'll hold back for now, and hopefully someone will grasp the nettle...