The idea that the goal of getting people to act like you want them to by providing incentive isn't somehow engineering by the government and thus less freedom is fundamentally flawed.The idea that government is curtailing your freedom by not requiring you to do anything at all is fucking stupid, plain and simple.
My freedom to not buy a new refrigerator is not being at all restricted because I could get a rebate from the government if I buy a new one. And my freedom was not restricted when I decided to get married because there are governmental benefits (note: I don't recall getting a check from the government, i.e. other people's money) attendant thereto.
It is how we work to get our children to do as we want as well, we either punish them for bad behavior or we reward them for good behavior.
It isn't more "free" because it is a "reward" (given from other people's pockets).
1. The government forces those who are not part of the "right action" to pay for people who are acting "rightly", by giving them direct monetary incentive (tax breaks). In the past they wouldn't "recognize" marriages between certain skin colors, among other things they worked to "incentivize", sometimes making them directly illegal (thankfully the courts struck that B.S. down). It's time to tell the government that such things are no longer their purview.
2. The government's idea of what compromises "right" action in such a circumstance (a person's choice on whom to spend a lifetime with) doesn't make it "right", that it would be based on what you personally think is "right" doesn't make it any more free either.
3. Taking others money (by force of government, including imprisonment) in order to pay people who act "rightly" (deserve the benefits that you otherwise wouldn't get) is not a sign of "freedom".
Government should never be in a position of "parent" directing your action by reward incentives based on either the religious "traditions" of the majority, or even just the majority's opinion of what is "right" (i.e. Multi-partner marriages).
This is simply the government working to control the most minute aspects of your life. That they do it by rewarding those people who act "rightly" with other people's money doesn't make it a "good" or somehow more "free" when they are directly taking by force of power money from some to give that incentive to others. "If you want to be able to visit your wife in the hospital then you just had better get licensed so you can. Plus we'll give you some of Bob's money if you do!"...
Rubbish. That isn't freedom.