An emotional shutdown is not an all-defence game based on glib responses and a stubborn refusal to talk about things. It is an outright refusal to engage.
A refusal to think about what the things people say or do mean because the inferences drawn might be unbearable.
A person in the state of emotional shutdown can be likened to a voluntary shut-in. One who does not venture out of the house due to unfounded or legitimate fears.
shut-in (def. as used throughout): a person in the state of emotional shutdown.
Glib responses require understanding where the other person in the dialogue is coming from. As thinking about intentions and goals is suppressed or even rejected by the shut-in, it is impossible to have any understanding required for deception.
The shut-in is not afraid of talking about things. That person is afraid of thinking about things, brooding over them, or going over them mentally. It is a defence mechanism that can be likened to the strategy of burning bridges to avoid unpleasant travellers and enemy troops.
Thus, the shut-in does not refuse to talk about things but talks without understanding what the other person is trying to get at. It is talk without any common ground. Ultimately, the person enquiring is unable to comprehend what the shut-in is trying to say. That person then will either disengage or sympathise but will not be able to understand. As far as the shut-in is concerned, such a conversation is a victory. No connections formed; mission accomplished.
Sometimes when others find themselves rebuffed in such a manner, they assume malice. But the shut-in cannot be malicious because they do not intend to cause any distress.
Naturally, this system breaks down from time to time. Memories seep through the defences and the shut-in broods over them in unbearable agony. Sometimes bits of conversation hit home and force a connection which consequently causes distress. Ultimately, the person in question is left without connections and has to live in fear. It is a lose-lose situation.