just talking about stealing candy does raise the probability they stole the candy. But once they're talking, confessing raises the probability they did it so not confessing should lower it.

Even if this is so, the total evidence that they're talking + they're denying may still raise the probability they stole the candy.

We rarely know that people express strong opinions about homosexuals, without also knowing what their opinions are. The difference with your example of the candy is that your wife initiated the talk with your son; your son didn't come forward himself and declare out of the blue, "I am against stealing candy!"