How to handle delusions?

My husband, who is in long-term care in the dementia unit, has periods of delusions that can be challenging to deal with. His current one, which I believe is based on his ongoing desire to come home, is that he needs to get on the train, that, in his mind, runs right by the facility. He can get very upset and defensive if he is challenged about anything, so we all (his family) want to say the least offensive comeback. Redirecting doesn’t work most of the time. How can we handle “You’re finally here! Come on, we’ve got to catch the train”