If you have proof, I don't see a problem with it being made public.
If we are talking about the 'T' word here, what's to say that a private approach will be better recieved than a public one?

But,

If all you have is suspicions, and they are made public, that invites the risk of accusations of paranoia.(until you can find proof of course, then abject apologies are due.)

On the whole, i think I go with the public approach. Better out in the open than behind closed doors.