A "useful antidote" refers to something that can counteract or help solve a problem or issue effectively. It is like a helpful remedy or solution. Full definition
Some were drawn to Nazism's exaltation of sacrifice for the fatherland, thinking it a useful antidote to modern individualism. (firstthings.com)
But the «Catholic» hope for Christian politics always acknowledged the reality of sin, too; and Tinder's more vigorous rejection of political hope may be a useful antidote to secular optimism even if it is not (as I think it is not) a true statement of human possibilities. (religion-online.org)
Although «a useful antidote to secular optimism,» Glenn Tinder's Political Meaning of Christianity takes too narrow a view of human possibilities, says Robin W. Lovin in a review of the book. (religion-online.org)