You might want to try this guide:
I've removed the warnings before but haven't tried it in a long time.
It just involves removing the VOB IDs that contain the warnings and stuff.
Here's the steps from that link:
With the tool Vobrator you are able to wonderfully check, which VOB-ID has got which movie, by previewing it.
So lets say for example:
VOB-ID 1 -> Warner welcome screen
VOB-ID 2 -> anoying copyright warning
VOB-ID 3 -> Sony production logo
To remove that copyright screen, load VIDEO_TS.IFO with IfoEdit, and in scroll down the VMG_Overview to the 'Menu language Unit' section.
Lets say for example, you see this:
Language menu Unit 1 [English]
Menu 1: [Title Menu] (entry PGC)
Menu 2: [entry only] (programs 1) (Cells 1) (uses VOB-IDs: 1)
Menu 3: [entry only] (programs 1) (Cells 1) (uses VOB-IDs: 2)
Menu 4: [entry only] (programs 1) (Cells 1) (uses VOB-IDs: 3)
Now simply 'one-click' on the line that contains Menu 3, and press the button 'Delete playback'.
You will see, that the line changes to:
Menu 3: [entry only] (programs 0) (Cells 0)
That's it. Save the Ifo file, and enjoy your DVD without anoying warnings.
I hope this helps.