Nah, kids deserve more credit than that. I'm honest with kids (to an age-appropriate level) because it's vital that they develop critical thinking skills. Considering the world they're growing up into, they're going to need all the training they can get to become able to discern fact from fiction.

I give kids legit reasons. I explore their "Why" questions. Then when I don't know the answer, I'll be honest but supportive, "I don't know, but let's find out." We have to model what being a rational adult is like, and how we come to logical conclusions. Children aren't going to learn this stuff from being brushed off or told some silly explanation.

That being said, it's important to be smart about context. It's reasonable and responsible to disengage from the conversation if someone demonstrates that they aren't arguing in good faith, whether they're an adult or a child. The problem is, a lot of adults jump to whatever explanation makes their own life easier, without any regard to how their response can shape the future adult they're speaking with. If you're truly concerned about kids' futures, you have to acknowledge that there is a lot you know that kids don't know yet. Offer them the benefit of the doubt and seize these opportunities to teach kids how to think for themselves.