Maksim Chmerkovskiy -- Hope Solo is LYING ... I Never Slapped Her

Maksim Chmerkovskiy -- Hope Solo is LYING ... I Never Slapped Her: Maksim Chmerkovskiy is adamant ... he NEVER slapped Hope Solo across the face behind the scenes at "Dancing with the Stars" ... despite allegations she made in her new book. TMZ has learned ... Maksim was absolutely shocked when he heard about the…