Don't have a solution to offer, but that is a real problem. There is a forum that I go to periodically where there are members who adore pitbulls. Quite often someone would write that even though they love their pitbull they would never trust it alone with other dogs. They always kenneled their pitbull when they leave.
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Joanne

Eli

Chipper

Eva

Snowboy

Rosie(R.I.P. 1996-July 29, 2013)

Cocoa(R.I.P 1998-April 26, 2012):