I virtually don't tell anybody. But I have a few friends who do know about my habit, and of course, my parents, since every now and then, I mail home a hefty-sized box full of anime/manga/CDs.
So - my parents. They'd rather have me listen to nothing after the 90s, but that's taking it too far. My dad doesn't mind. He's too much of an individualist.
I dragged my mom with me to an anime musical(!) and to the SKE shop this past January straight from the airport (so that involved a Shinkansen ride), and she was beyond annoyed that I was still listening to "teenager stuff" and more importantly, spending craploads of money on photos and CDs and DVDs. Then again, it still is her money, and when I use my own money, she's only concerned with the amount of time I spend on it (fair enough). Otherwise, she does recommend me to practice the dances as a means to stay in shape.
But she hasn't seen any wota in person yet, so I dunno...
My friends either don't care, or they dislike it. I hauled my friend (who was in JET that time) to a concert and she didn't talk to me for months. But she acknowledged Ai-chan and C-ute's talent so that's okay.
Another friend of mine is really into SNSD and when I played for him SKE48, he said it was "too recycled" and "old fashioned".
A third friend of mine wanted to get into Jpop and I played for her a couple of SKE48 videos. I probably should have chosen something better like Hirai Ken or Ayu or just good old fun like Yuzu. She wasn't disturbed by the swimsuits, but more by the fact that there were so many people crammed in the video. Oops.
tl;dr - they're mostly indifferent, or don't listen to anything outside their own favorites (I have a friend who refuses to touch anything beyond old 60s live music), or they think it's just dumb.