Yes, it will and it is hurting straight marriage everyday in many, many ways. First and foremost, promoting 'gender confusion' which leads many men (and some women) to question their sexual orientation,  and consequently reject both the responsibilities and rewards of heterosexual marriage; i.e. the procreation, birthing and raising of new human beings. Without strong support for heterosexual marriage, family formation and the generation of new and psychologically healthy children will seriously diminish. It's already happening . . . The 'gay' lifestyle is truly a 'dead end' that does not benefit the larger society in any way.