No one said this.
I thought your point was intent. Most people would not say to hide Jews from Nazis was bad faith I think.
That would be perfectly bad faith to the Nazis. There's no such factor as moral good or bad here; bad faith has more to do the intent you have towards each party. If the intent is to explicitly trick someone towards something you want or away from something you don't want, that is usually in bad faith. (There are some exceptions.) If the intent is just to explain something in a way others will understand, even if your explanation turns out to be (knowingly) inaccurate, that can sometimes be in good faith, though I wouldn't call it good practice.
And the intent here is to intentionally mislead, so how is that not bad faith?
1. A is lying to B, and they know that B doesn't know the truth. The intent is to make them believe the lie, which is intentionally misleading them and bad faith
2. A is lying to B, and they aren't sure if B knows it's a lie. The intent is to make them believe the lie, which is intentionally misleading them and bad faith
3. A is lying to B, and they know for sure B knows it's a lie. The intent is either to provoke an emotional reaction from either B or someone observing (which is bad faith), or performative for others who will see the lie and might fall into categories 1 or 2, which is bad faith
I don't understand how anyone could plausibly argue that lying to someone intentionally isn't bad faith. Maybe I'm the one falling for category three here
For example, if I lie to protect both myself and all other parties involved, that sometimes can be in good faith! It can be bad faith if I know that it hurts them and also know a less hurtful alternative, but if I really believe the less immediately hurtful alternative will lead to a worse overall outcome then I can still be acting in good faith. It's really a lot more nuanced than "deception bad". I have to deceive myself all the time to achieve good outcomes! now I wouldn't say my treatment of myself is good faith but I try sometimes.