be for/in a good cause
be for a good cause
To have a beneficial, often charitable, aim or effect. Oh, the money's going to charity? Sure, I'm willing to donate a few bucks, since it's for a good cause.
be in a good cause
To have a beneficial, often charitable, aim or effect. Mom just wants to keep you out of trouble—her rules are in a good cause.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
be (all) for/in a good ˈcauseworth doing, because it is helping other people: Most motorists seem to accept that the speed cameras are all in a good cause (= they help to keep people safe on the roads by stopping people driving too fast).
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