I don't think the real problem is people not wanting a campy movie: they don't want a campy movie in the same continuity as a more serious work. It's the same problem people had with Superman 3 (since, even though it was Richard Lester's slapstick genius "unleashed", it was STILL a sequel to Richard Donner's "Superman"), and the 1998 "Godzilla" (which was outright loathed until the creators confirmed the monsters wasn't THE Godzilla, but just "Zilla") - "Batman and Robin" would've worked fine if it was declared a spin-off or parody of Tim Burton's "Batman", or even as a straight movie adaptation of the Adam West TV show. It's just that fans couldn't accept it being part in the same universe as the nigh-legendary Tim Burton "Batman".
So if you are trying to get a friend to watch "Batman and Robin", just tell them that it isn't a sequel to Tim Burton's "Batman" (or if they know that it is, tell them they shouldn't ACT like it's a sequel, and take the film on it's own campy merit), then you'll be in for a fun movie night experience.
And if they STILL think it's bad in spite of what you told them, punish them by showing a genuinely godawful movie like "Howard the Duck" or "Garbage Pail Kids".