The navigation bar can be useful depending on your page and what you want to accomplish. My point was, that your solution isn't suitable if you want to hide the bar on one CMS page, because your code affects them all.
It's like the author asked to remove a tree and you suggest to burn down the entire forest. Sure, it gets the job done, but also slightly overshoots at the same time. No offense, though
Yes, no problem, its a different opinion 
I totally agree with you with that, it affects all CMS pages, but in some cases, it's not a problem 
In this case, there is some subpages, so it's not recommended because it will be hidden on all pages and subpages..