I'm not so sure he can make it back from this, but not because of what Mel Gibson said:
According to the [Los Angeles County Sheriff arrest] report, in addition to threatening the arresting deputy and trying to escape, Gibson said, "The Jews are responsible for all the wars in the world," and asked the officer, James Mee, "Are you a Jew?"
As vile and as ignorant as what Gibson said was, it's not enough to destroy his career. There are two reasons for this.
First, a lot of Hollywood is populated by Bush-hating ranters cut from the same cloth as Michael Moore and Alex Baldwin. These people have no love for Israel, and by extension, for Jews in general. They're just smart enough not to get drunk and yell at a sheriff's deputy while being arrested.
Second, Hollywood seems to tolerate a lot. Woody Allen has a common-law relationship with Mia Farrow, helps raise Farrow's adopted daughter Soon-Yi, has an affair with Soon-Yi, and then marries the girl thirty-five years younger than him. He was not Soon-Yi's biological father, or her adopted father, but most normal people thought Allen was cutting close to some sort of incestuous pedophillic relationship. But he still makes movies and people still call him brilliant.
It's not clear how old Soon-Yi was when Allen starting having sex with her, but in the case of Roman Polanski, the facts are not in dispute. In 1977 at age 43, he pleaded guilty to having sex with a 13-year-old girl after drugging her with a combination of champagne and quaaludes. Fortunately for Polanski, he had French citizenship, and in grand French tradition, ran away. But he still makes movies and people still call him brilliant.
So why can't Hollywood turn a blind eye to Mel? It can, of course, because it has done so in the past. But Mel Gibson has made enemies. The Passion of the Christ was made with his own money outside of the control of the Hollywood studio structure, then went on to make millions. It proved that an ostentatiously religious movie with a positive moral theme could be successful, even without a car chase or robots from the future. That threatens the Hollywood establishment. In this age of cheap digital cameras and editing software that can run on a home computer, every Cecil B DeMille wannabe can make a movie. If people start making successful movies without the studio imprimatur, well, dahling, that's the end of civilization as we know it.
That's a lot scarier to these people than anti-Semitism or pedophilia. And if Mel Gibson goes down in flames over his arrest and his subsequent ranting, I figure it'll be because of this more than anything else.