This is only true if you take an uppity attitude when talking about music with people less familiar with non-top 40's music.
If anything, /mu/ has accelerated my taste and interests in music and I've been able to share that with some friends that have agreed likewise.
Instead of, "Wow shit-tier pleb. How the fuck have you not heard of so-and-so?" rather "That's cool, man. I'm not really into that stuff, but if you like so-and-so, you'd really be like this-and-that."