You're 100% correct. I checked this with Houdini, to see if there were any tactics you were missing, and there is not. White wins a pawn and probably the game... he now has a minor but significant advantage. The author overlooked this, surely.
Mistake in Silman-Minev, Portland 1984
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Just for fun I had to strong engines (Stockfish DD and Houdini 4) play a small, 10 game bullet tournament from that position. (After White plays 8.Bg4)
White never lost and managed to win four of the ten games. (I actually expected more wins than that, but it was just a bullet tournament, after all.)
http://www.chess.com/chessmentor/view_lesson?id=2448
The very last move in this lesson (8..Bg4?) is a mistake that loses a pawn without mention of how to play. I was reluctant to play 8...Bg4 because white can play 9. Bxg4 Qxg4 10. Bc5! and Black loses a pawn by force because if 10... Bxc5 11. Qxd5+ and the bishop is forked with subsquent checks to follow. Can someone tell me if im wrong?