Shia LaBeouf Band -- We're PROUD of His Penis

Shia LaBeouf's wang is getting some major support after it made its debut in a new music video for Sigur Ros -- with the band telling TMZ, "Icelandic people are not prudish about people being naked."

The artsy video -- which features a few side profile shots of Shia's LaPenis -- went viral right after it was released on the Internet Monday morning.

Now, Georg Holm, the bassist for the band, tells TMZ, "At first I didn't know what to make of the video, because it is so full of ideas and confusion."

But after seeing it a few times, Georg changed his opinion ... saying, "Now I love it. It seems to have no beginning and no end, and just makes you think about what might and might not be going on."

For the record, Shia is credited with collaborating on the video concept -- which, according to the director, is an artistic interpretation about the struggles of various addictions.