Granted, there are many in the modern Reformed community that are enamoured with “pluralism” within the broader society, even the extremist tolerant views of folks like Horton.
Why that is considered biblical or superior to the alternatives is the real question.
The great majority of evangelical-conservative Reformed scholars I know of (like the big-guns I listed above) would turn the question around, and ask why confusing Old Testament Moral and Civil Law (as since the book of Acts the Church is, and has been, only accountable to the Moral) is considered by some to be Reformed?
Why for example do we suffer a Witch to live (Exod. 22:18)? Or were the residents of Salem, Mass., right?