It's not about "speaking publicly", it's about claiming (implicitly, typically) that Science supports a particular side in a political debate. Science very rare

It's not about "speaking publicly", it's about claiming (implicitly, typically) that Science supports a particular side in a political debate. Science very rarely actually has the power to do that - it can advise on how (probably) best to achieve a given outcome under certain constraints. The political debate of Sagans time was unilateral nuclear disarmament and it fed eagerly on accounts of the horror of nuclear war. The unstated constraint was that it was perfectly happy to accept a significantly less restrained Soviet Union on the world stage. Science can't tell you if that's a good idea or not.