I don't remember Viv making such a statement.
Keep in mind that Tear It Down was the B-side to Women (the first single off Hysteria) in 1987 so that song goes back a lot further than the re-recorded LP version on Adrenalize. Tear It Down was popular enough on it's own because a lot of radio stations gave it airplay due to requests.
But the original B-side version of Tear It Down would have been released while Viv was still in Whitesnake, so it's possible he could have made a comment about it. It was recorded in just a few days, so it's not like they gave it the full Hysteria production treatment. Fans loved the song because it was a straight ahead AC/DC-style rocker.
By the time Leppard were invited to perform on the 1989 MTV Video Music Awards, they played Tear It Down!
http://www.youtube.com/watch?v=HbOBMl42qw8