I figured out a trick to bypass them anyway. This only works if the ads come up when you first start playing the disc and not at any other time.
1. Stop the DVD.
2. From the main screen of your DVD player, with the disc not running but in, hit the "Jump to MENU" button.
You'll immediately be at the main menu; it's how I bypassed all the ads at the start of the disc.
Gah. Why the fuck do advertisers think we'll react favoribly to an advertisement forcibly placed at the start of a disc I already paid for? And then they have the balls to force us to watch it every damn time? Anyway, it's nice to defeat their little "You can't fast-forward here, bitch" trick. I figure it's probably obvious and standard and everybody does it, but I felt like posting about it anyway. So there.