Did Zach Galifianakis Torpedo Mel Gibson Cameo in The Hangover 2?

Mel Gibson was set to play a small role in The Hangover 2 until the film's producers unexpectedly cut Mel's cameo, citing unrest among the cast and crew.
It's unclear who specifically objected, but rumors are swirling that Zach Galifianakis - whose Hangover quotes pretty much made the original - is behind it.
In a Comedy Death-Ray Radio podcast October 15, Zach lamented that, as an actor, "you don’t have a lot of control" over elements of a film's production.

Moreover, "I’m in a deep protest right now with a movie I’m working on, up in arms about something," Galifianakis said. "But … I’m not making any leeway.”
Combined with director Todd Phillips’ comment that Gibson “did not have the full support of my entire cast and crew,” you can see how that rumor started.
Galifianakis' manager had no comment on this, nor did Phillips, who was excited to have Gibson on board. The move has sparked outcry from some fans.
Supporters note that Mel, despite his issues, hasn't been charged with a crime, unlike Mike Tyson, who had a role in the first Hangover and raped someone.