The filmmaker insists the actor - who was questioned by police over the alleged assault of his mother and sister - is a "big-hearted, good guy" who is always professional on set.
Speaking at the Comic-Con convention in California, McG showed his support for Bale, saying: "Just for the record, he's a big-hearted, good guy - and I've worked with a lot of people - that's just simply who he is."
"He's the most professional, passionate actor you're ever going to find. I mean it's just that simple."
McG also revealed Bale is dedicated to his wife Sibi and their three-year-old daughter Emmeline.
He added to People magazine: "Bale is just all about the work. He loves his wife, he loves his child, he loves being an actor. He's not interested in materialist things. He wants to come to work prepared."
Bale is currently working with McG on the fourth Terminator film, in which he stars as John Connor.
In the film, Connor leads a human rebellion against a group of robots who have taken over the earth.
Bale stars in "Terminator Salvation" alongside Anton Yelchin, Sam Worthington and Bryce Dallas Howard.
The film is set to be released in summer 2009.