Pick any book, story, poem, movie or heck, how about a song? Pick something you truly can't stand, and analyze it a bit. Do you hate it because the lyrics are terrible, because the characters or flawed, or because you had a boyfriend who loved it, and even though it's pretty good, you can't read it again because it will remind you of him and he was kind of an ass?
This is your chance not only to rant (don't we all need a couple of those) but also to find legitimate reasons to despise something, not because we said so, but because it requires development in very specific areas. It's ok to hate something if you're an expert on it right? And all critics are experts. We know that. If nothing else, you can make your rant sound more intelligent and thus, a believable argument.
What are the components that seem flawed to you? Or underdeveloped? Or misled? Or just plain inane and obtuse? Is it boring? Is it too pretentious? Too immature?
Is there anything redeeming about it? (a good rant will give at least one of these, to show that you're a good sport).