When you installed the Dyn Updater, you were being asked if you want to use their DNS service or not. You apparently answered with yes. You got what you decided.
That may be so, but that means they weren't descriptive enough about what that setting was doing. Either way, it's one thing for the software to change your DNS settings one time, when you first allow it. It's another to prevent you from restoring your own settings without realizing/remembering they were being overwritten by Dyn software. Even the help text for the setting in Preferences isn't explicit enough about what they're doing. All it says is "...this machine will be set to use Dyn's Recursive DNS service instead of the ones provided by your ISP." Sorry. Anyway you look at it, this is bad practice and poor implementation. As I said in my OP, the behavior is virus-like.
Not to mention the fact that it makes one of the most popular browsers in the world, and a few other apps, stop working correctly.