Sexual Orientation does not create more instances of sexual child abuse. A parent should love their child no matter what gender they find physically attractive. A twisted individual is going to cause harm to a minor weather that are gay, straight, or bisexual. A pedophile doesn't go by sexual orientation.
The thought that being Gay or Lesbian would make you more prone to perpetrate incidents of sexual abuse is just not true. It probably fits in well with certain religious agendas that seek to alienate gays and lesbians from having the same basic civil rights as heterosexual people. There is absolutely no statistics that back the assumption.