Angel did actually refer to Connor as a "snack" at one point (because of the W&H blood-spiking). This came at about the same time as the last of three warning signs in the false prophecy.
On top of everything, the implication was that Wes wasn't getting much if any sleep since he translated the prophecy, which can really affect your judgement.
I think he *was* guilty of bad judgement in not confiding in anyone in AI. Cordy was in Mexico, true, and he had been burned by the Fred-and-Gunn thing, but IMHO the situation (if it had been true) was bigger than that. And there was always Lorne, who was enough of an outsider to stay relatively detached about Angel, plus had all sorts of demon connections that might have been able to double-check the prophecy.
It's the kind of "tragic mistake with snowballing consequences" that has to occur at least once a season in Whedon-land.
(On the other hand, I think the AI members other than Angel were being bewilderingly unreasonable or passive about ostracising Wesley. They could have talked to him without involving Angel.)