Mel Gibson and Oksana Grigorieva left their newborn daughter Lucia Anne at home for what should have been a relaxing, romantic dinner at Giorgio Baldi, which turned ugly when Mel became incensed and threatened a photog!

While waiting for his car, a waiter from the restaurant came outside to get his signature on the bill, but Mel became agitated having to wait for his car and stepped up into a photog's face!

"Don't you dare touch me," Mel said with a weird smile on his face, getting as close to the guy as he could. It's almost as if he was looking for a fight!

Luckily, his car came at just the right time, and Mel backed off to jump in with Oksana.

I guess Octo-Mel's getting cranky from spending too many nights up with a one-month old!