Reynolds is not applicable. Utah was a Territory, Utah did not become a State until 1896. There is quite a bit of difference between a Territory and a State.
The applicable case law couldn't be clearer, for example, as Justice Frankfurter explained in his concurring opinion in Williams v North Carolina:
[i]"The Constitution of the United States, however, [b]reserves authority over marriage and divorce to each of the forty-eight states.[/b] That is our starting-point... We are not authorized nor are we qualified to formulate a national code of domestic relations.There may be some who think our modern social life is such that there is today a need, as there was not when the Constitution was framed, for vesting national authority over marriage and divorce in Congress, just as the national legislatures of Canada and Australia have been vested with such powers. Beginning in 1884, numerous proposals to amend the Constitution to confer such authority have been introduced in Congress. But those whose business it is to amend the Constitution have not seen fit to amend it in this way.[/i]
Homo-activists are the ones pushing to ignore established precedent and make marriage subject to Federal Control, when it has long been delegated as a State Power.
They want Courts to do what the activist Court did in 1973 with Roe and establish homo-"marriage" nationwide via fiat. Short of that, they want the Courts to ignore established precedent and allow one State to make public policy for the rest of the State via a faulty reading of the FF&C Clause.
And they may very well have five votes on the SCOTUS to do just that.
That's the risk.
"Laws are made for the government of actions, and while they cannot interfere with mere religious belief and opinions, they may with practices. Suppose one believed that human sacrifices were a necessary part of religious worship, would it be seriously contended that the civil government under which he lived could not interfere to prevent a sacrifice? Or if a wife religiously believed it was her duty to burn herself upon the funeral pile of her dead husband, would it be beyond the power of the civil government to prevent her carrying her belief into practice?""Can a man excuse his practices to the contrary because of his religious belief? [98 U.S. 145, 167] To permit this would be to make the professed doctrines of religious belief superior to the law of the land, and in effect to permit every citizen to become a law unto himself. Government could exist only in name under such circumstances."