This is not really about honesty - if someone asks your opinion you can explain your concerns diplomatically - but if they don't then you can also keep quiet.

This is not really about honesty - if someone asks your opinion you can explain your concerns diplomatically - but if they don't then you can also keep quiet. It's more about whether you're going to actively point out a problem with a plan that someone higher up than you is trying to take credit for. i.e. they will feel personally attacked - that their judgement is questioned - when you speak up. It's an extremely difficult thing to do without making enemies and enemies last a long time and 1 enemy is more damaging than can be made up for by lots of friends.