Political Memes

Something to consider on two fronts.

1. Parents being of both sexes is not terribly important for long term child raising. Same sex couples sometimes choose to adopt but they often have the capacity to have children themselves without assistance of a medical body and often with the help of friends or compassionate donors. There are a lot of gay folks whose names are on the birth certificates of their kids because they did the deed the old fashioned way in the interest of having a kid. They maybe just didn't enjoy the process. This doesn't present a problem legally because mechanically speaking people have kids out of wedlock or split up amicably all the time and the mechanisms for transferring parental rights are pretty much the exact same.

Also your concerns are not new. They are also not unstudied. It has been studied extensively. Science has found there is no meaningful difference between the outcomes of being raised by a same-sex couple as a mixed sex couple. They measured their rubric across a number of success variables across physical wellbeing, mental and emotional health, acedemic outcomes and so on. Basically if you are raised by adults who show affection, are responsible and committed to the wellbeing of the child it doesn't really matter what their sex is. At some point trusting a body of science is nessisary over one's gut feelings or supposition.

Here's a study with an approachable abstract to get you started.

https://pmc.ncbi.nlm.nih.gov/articles/PMC4091994/

2. Marriage exists in a number of cultures, its functions even in a traditional sense are not always religious in nature and not all cultures that have marriage have bans on same sex couples marrying. Religions can also be newly formed and are still valid. Banning same sex marriage is in effect favouring some religion over others. Christianity does not have a monopoly on the concept of marriage as a religious feature. When a religions (ie Christian) reason is given to enforce a marriage ban it stops other religions from being able to properly function. Gay marriage being federally allowed does not stop Christian denominations from being allowed to refuse to marry couples under the beliefs of their religious creed.