I doubt if they will ever post their "policy" regarding stopping guests without children. . . wouldn't look good hanging there on the wall or sitting on the check-in desk. Not very politically correct, even though we as parents demand that our children's safety be first and foremost.
I think you should, if you have not, give Nick hotel some feedback regarding your experience. As everyone always says, if there is a problem, let management know otherwise they can not correc it. Maybe you should give them the opportunity to explain to you why they did what they did and do something to make things right. They need to know how offensive their actions were and how they made you feel.
Can I dare ask how the hotel was otherwise? Pool area, arcade, restaurants, etc. How was your room? I read your report, but there weren't many details regarding these other things. I'll go back and take a look at your pics again. I glanced at them, but only had a few minutes to spend. Again, I'll be looking out for their security and how they interact with guests while we are there, but I am wondering if there are other things I should be looking out for.