Salam Fadiva,
My humble understanding is we should not worry about people getting fooled or misguided by tricksters. No matter what tricks a disbeliever play, they can not fool Allah. And Allah is the one who guides and misguides. Therefore, if a person is already misguided by Allah then that person will fall prey to all the tricksters. If a person is guided, then no matter what the trickster does, they can not be fooled. Allah gives people many chances in their life to come to his path before they are marked as misguided, people are not as innocent as they appear. We do not know what they hold in their soul. So don't focus on people being misguided, that is Allah's business, let us focus on if we OURSELVES are misguided or not, it is very hard to self reflect on ourselves.
Also the one who gets fooled becomes the trickster himself. For example when a parent teaches the child that Jesus is God (when the Quran says that believing such a thing is one of the most worst thing, the world shakes), then the parent has become a trickster to the child. No matter how much the parent love and care for the child, the parent is actually a curse once they teach the child such a wrong thing.