I'm a college junior, almost turning twenty-one and I go to an all-girls college. Which all seem like relatively normal statements, except for the fact that I'm also engaged. I've been dating my now fiancee for forever and a day, and I love him more than I ever thought I could love someone. Back home it's not a big deal. People know us. They know we are engaged, that we go together like peas and carrots, and that this isn't some stupid teenage love thing. But in school and especially at work (which is mainly with teenagers), I get some pretty crude responses. Once a guy at work asked me if I was dating someone (I had a diamond ring on my hand... I thought it was glaringly obvious) and I simply said," I'm engaged," and smiled and tried to move on with the subject. Instead he said," Oh my God. How do you know if you actually love the person. What are you, like 19?" Now, in a way I know I'm asking for it. People usually aren't engaged at my age, but the responses (which I once assumed would be happy, joyful, or at least a little bit pleasant) are of pure shock and horror. Everyone that is close to me is excited, but the people who aren't in the situation freak the heck out. I know I should blow it off, but sometimes it's hard. What should I do if someone gives me a hard time?
For starters, you should stop assuming that people are giving you a hard time about your engagement when you could just as easily assume that they're merely surprised by it.
Don't get me wrong, Sparkler: I'm sure that you've encountered your share of obnoxious, condescending responses to the news of your impending marriage. But it's also clear that you're way too ready to take offense when people don't give you the positive reaction and validation you expected—and that your expectations, at least when it comes to your peers, are pretty unrealistic. For instance: the fact that you thought it should be "glaringly obvious" to a teenage boy that you were wearing an engagement ring is, and I mean this in the nicest possible way, complete and total lunacy. Guys your age aren't going to look for a ring on your finger before they ask if you're dating anyone. They just aren't.
The truth is, prevailing cultural norms being what they are, you'll probably be the first and only person these people ever meet who was engaged before the age of 21. (The average age of first marriage in the U.S. is 27 for women, and 29 for men.) You're very unusual! And when people encounter unusual things, they often react with surprise. So if you're going to get your underpants in a bunch every time someone says "Whoa" instead of "Yay" to the news of your engagement... well, I hope you enjoy bunchy underpants.
That said, some people no doubt are freaking out when you tell them, and here's why: for you, your engagement is a personal choice, and an awesome one. But for other people, and particularly people who aren't super comfortable with their own lives, it's an uncomfortable reminder of the insecurities they feel about love, marriage, and life milestones. And when those people are immature, dumbass teenagers who feel insecure about everything anyway, then yes, some of them are going to say stupid, insensitive things.
Because like you said, these people don't know you; they're reacting to the idea of being engaged at age 20, not to your engagement in particular. So when someone says, "You're getting married? What's wrong with you?," what they're really saying is, "But I'm not there yet! Is something wrong with me?!"
Which means that there's no point in getting defensive; your best bet is to either shrug it off ("I know it's unusual, but we're psyched"), or crack a joke ("Well, he's a 100-year-old vampire and he says we can't have the sex 'til we're married"), or say, "That's an interesting reaction," and then change the subject. But what I'm really hoping is that you'll realize the pointlessness of expecting or seeking "happy, joyful, or at least a little bit pleasant" validation of your engagement from the world at large. You won't get it, and moreover, you don't need it; you're getting married, and the only person who has to be thrilled about that is your husband-to-be.
Oh, and congratulations.