Sometimes it just seems futile. Every day I see top comments on youtube that try to promote unity between metal fans, and every day I see them grossly outnumbered and outvoted by people spewing contemptuous bile towards other genres of music. Don't be those people. Don't write those things and don't vote them up if you see them, it's not helpful to us OR our image.
In the spirit of unifying metal genres, check out this awesome video, done by a guy who actually knows his genres. And god bless the commenters, they come so close to not being dickbags.