To dc$, believe me everyone here has done exactly what you have done in our lives. And, almost assuredly, far worse. The difference is, we did it with a whisper to a friend or with a barbaric yalp with our posse, clique, group of malcontents/misfits/sport team--whatever. This newfangled interwebs thingy is confusing to us when a whisper/yalp to friends can be spread to all in a moment for them to do with as they will. We fear your power to communicate with anyone and everyone with ease with whatever you choose. An internet meme can change the world.
Personally? I don't think you did anything wrong. I think a part of growing up is learning to challenge authority appropriately. I think the public square is best place to make those challenges. Putting ideas out into the open....well, look at my signature quote. We can only hope when all look at things stupid is squashed and enlightened is lifted, even though we know with the nature of humankind the reverse can often happen because of petty issues. One price of freedom is you have to accept the problems with free speech if you want to savor the benefits. The problems are multiplied when speech can simultaneously reach an entire population—or appropriate sub-populations based on whatever criteria people self-divide. While I have grown up through the explosion of computers to the internet and have a pretty good understanding of the technical issues of how it all works, the sociological changes are simply not in my heart. I don't think anyone over a certain age understands how things are different today.
All that being said, there are many complications as well. Look at the cases I've cited and follow the relevant cases the courts cited too. If you read the three fairly recent Supreme Court cases regarding student speech, you'll find how the courts try to address the issue for everyone even before they know what the specific facts are of what happened when we ask similar questions later in life. You'll find the issues get down to if the speech is in school or out (and what that means) and what types of speech can be actionable by the school. (A good page with summaries [I recommend going to the actual cases, however.] is at: http://law2.umkc.edu/faculty/projects/ftrials/conlaw/studentspeech.htm ) The cool thing is, I GUARANTEE you could get a paper or research project out of it for some class. Think of it, homework which is fun! Not only that, you will learn much more. You will gain power. Use it well.