The moral thing? NOT to use a weapon that likely won't work, and in the process NOT provoke the Borg into a REAL invasion that will DEFINITELY kill billions.
I swear Anwar, you are more repetitive than a broken record. You keep saying that BUT WHAT IS YOUR PROOF? Picard should have done the right thing and released that virus. He and his entire crew believed the virus would have worked, so IT DOESN'T MATTER IF THE VIRUS WOULD HAVE REALLY WORKED OR NOT! Secondly, IT DOESN'T MATTER IF YOU "ANTAGONIZE" THE BORG OR NOT, IF THEY WANT TO SEND A THOUSAND CUBES TO ASSIMILATE THE FEDERATION, THEY WILL DO IT REGARDLESS OF WHAT WE DO TO THEM!
Picard did a foolish thing when he let Hugh go. Once again, Picard displayed total moral cowardice.