If other teams were still realistically involved in the title battle, I can see why Brawn's top brass would get involved. As it is, Red Bull are pretty much out of things - certainly the constructors' championship and almost certainly the drivers' title - so Barrichello and Button should be allowed to race as they choose, so long as they don't take out one another in the race.

Ayrton Senna: WDC 1988,
1989, 1990, 1991
McLaren: WCC 1974, 1984, 1985, 1988, 1989, 1990, 1991, 1998,
1999, 2007McLaren: WDC 1974, 1976, 1984, 1985, 1986, 1988, 1989, 1990, 1991, 1998, 1999, 2008