When I was married to my ex, for my own survival, it was sometimes necessary to "bend" the truth. I'm not proud of it - I don't condone lying in my home and I try to promote honesty in my children. However - sometimes - to avoid an inevitable reaction from my ex and protect myself, I would lie or conceal the truth.
If he was working I a weekend, I either wouldn't make plans until after he left, or I wouldn't tell him about them. Not that I was doing anything that merited any interest. Usually it was just shopping or heading up to my mom's.
He'd ask about ingredients in our son's food. Not from an educated - this is bad for my son standpoint, but from an OCD, panic, I read this in an online magazine standpoint. I would lie about the ingredients to placate him. Or I'd feed our son the stuff he was worried about when he wasn't home.
All coping behaviors. Designed to protect myself (and our son) from increasing amounts of bullying. If I didn't - I would face an onslaught of yelling and demeaning remarks.