How would removing rights granted by marriage and putting them under a civil union, which is what I took the parent to propose, supposed to not trigger irrational excitement of people who support marriage in it's current incarnation? You can argue that people shouldn't care if they just have to get a civil union in addition to their marriage, but we've already brought irrationality with regards to how marriage is defined into the argument as a behavior that we agree exists, so we can't ignore it now.