I couldn't agree more! This is what happens when lawyers pretend they're economists. The mini-golf example is a perfect one to use to demonstrate the problems with this analysis: while the cost will be borne by all, the benefit goes to few. The inability (both structurally and legally) to price discriminate between those who benefit from the access and those who don't, means for accessibility to work, everyone must pay for the increased costs.
Many mini-golf businesses are likely near break-even. They spend a bunch of capital up front and then charge rents for a round of golf over time to pay for the capital. If they are already optimally priced (the price they charge generates the maximum amount of revenue possible) the new requirements will reduce their profits. If those profits fall below the cost to build and pay for a new mini-golf location, it either won't get built or will go out of business.
The weird means justification analysis Justice did is insulting. Why can't something be justified simply because it is "the right thing to do"??