At First, you can skip to install it, but the time comes that you don't have an option but to install it! Facebook is forcing you to install it.
So here the a brief tutorial how to get rid of the annoying Facebook Messenger.
First.Go to settings.
Under the "Device", go to Application Manager

You can now click on "Clear Data".
You can now lauch again the facebook application. You will be logout, so you need to login again. You can now continue using the Facebook old messaging.Note: This method is NOT PERMANENT but you can always do this at times you are forcing to install the Facebook Messaging app.
THIS IS THE UPDATE
I notice that this method is stopped working to my phone. I figure it out. I didn’t notice that I updated my Facebook app.
Here's the fix.
Uninstall you current Facebook app (and fb messenger if you download it)and install this Older Version of facebook.Click Here


