LOL. I remember this argument in college. And you are correct, everybody makes their own meaning (more so on post modern and later literature, but that's the point of that genre, no?). So? Did you have a bad experience with a professor who got upset that you didn't see the same meaning?
I was actually part of the very experiment you described (again, in college). We found that interpretations varied widely. It was both frustrating and fun. It taught most of us that even when given the same input, people would come to hugely different (and often equally logically valid) conclusions. One reason for this is past experiences. Knowing all this helps me all the time; how else can you explain logical, reasoned analysis of the same input leading to both Smart Conservatives and Smart Liberals? Both have equally defensible points logically, but their starting interpretations of the data are so divergent that they're unlikely to agree. If you can find the divergences, one can better figure out how to re-frame the starting arguments to bring them both to a more agreeable position.
Example: Randall Munroe. I interpret that comic as a dig against literary analysis, but not a definitive one. Randall appears to see everything in life through the lens of mathematics, making Deconstructionism, a highly interpretive practice which is heavily influenced by Philosophy, as unintelligible to him as mathematics above 7 dimensions was to me. However, I can appreciate both his frustration and see how he can be just like the nincompoops who think that since they don't understand the equations behind how quantum foam behaves near an event horizon that it's both useless and meaningless (just in reverse). We all do it sometimes, and it doesn't make me dislike XKCD (it is the only comic I read religiously), but it seems we have different takes on this strip.