Wow, am I alone here? Man, this stereotype is so insignificant, flossing my teeth is more important.
It's a trivial stereotype and, in my eyes, anyone that gets offended by trivial stereotypes is way too sensitive. It reminds me of that old saying "Sticks and stones break my bones." There are some stereotypes *that* can affect your life negatively, such as that sickening 'all Muslims are terrorists' and other stereotypes that can lead to discrimination (e.g. airport security). But honestly, the stereotype 'men are horn dogs' has NEVER deterred a woman from being my friend, as far as I know (and anyone that lets that stupid stereotype deter them from getting a male friend isn't worth being friends IMO). Seriously, it's never once made an impact on my life in anyway, even in the slightest way imaginable. There are some serious stereotypes out there than can genuinely cause discrimination for people, but instead men are on the internet complaining about stereotypes as insignificant as 'Brits have bad teeth' or 'Americans are fat.' Some do, some don't; why on Earth are you letting it get to you?
As for a 30 year old teacher sleeping with an 18 year old boy: He's legal, she's legal -- What's the problem? As long as it's not illegal it's absolutely no one else's business. The police and the parents need to stay out of his sexual life if it's consensual and they're both legal age.
Oh, and I saw the video on that link in the OP and I thought it was absolutely hysterical. It's absolutely DEPRESSING that there are men in the world that get's upset by a video like that.