Can't turn off in-app browser for messages app

[AC Question]

My messeges app on my Galaxy S6 (6.0.1 OS) recently decided to have an in-app browser, which I don't care for. Found the setting to change it in the app manager, but it's greyed out.

 

[Sim-X]

I also have the same problem on my GS7 edge Sprint version. Very annoying, why would it be grayed out for? Anyone have a solution?