It sounds like everyone here draws a distinction between civil and religious marriage and allows that churches can define marriage however they choose (even if one finds their criteria repugnant.)
Further, most here seem to be of the opinion that civil marriage is a right and as such, the government should not preferentially grant this right to some groups over others.
The government affords tax advantages to marriage for one reason: to incentivize the raising of children in stable homes. The idea being that these children will grow into consumers and workers, both of which are essential for a growing economy. It was an acknowledgment of what Piggs have said repeatedly: raising kids is difficult and costly.
So my question is: Is this incentivizing of child rearing unnecessary and/or immoral? If no such incentive exists, then should there even be a legal recognition of any marriage (what I’ll call the “tg option”.)