He's saying that in a politicized world (like the one we live in) the use of the phrase "no evidence" is a sign that the author is lying to you. He's claiming

He's saying that in a politicized world (like the one we live in) the use of the phrase "no evidence" is a sign that the author is lying to you. He's claiming that if you if read a story by someone in power which claims "No evidence for X", you should update toward "X is probably true but politically inconvenient". He's not claiming this is logical, only that empirically it's a good strategy. A parallel might be that if the board of a company in the midst of a scandal puts out a statement saying "We have full faith in the CEO", your actual conclusion should be that the CEO is on their way out. This isn't what the words mean, but in practice it often turns out to be the right bet to make.