It is not whether the charge is true or not it is the seriousness of the charge that must be responded to.*
* Dan Rather
Actually it was Tom Foley who said it first.
“We have no conclusive evidence of wrongdoing, but the seriousness of the allegations, and the weight of circumstantial information, compel an effort to establish the facts.”
http://www.nytimes.com/1991/08/06/us/inquiry-is-ordered-on-1980-campaign.html?pagewanted=all