I’m not a parent but a teacher who has encountered similar things with students. This won’t work in all the situations you described but you can try giving them affirmation by telling them they are very creative for coming up with cool ideas or stories. This can provide positive attention without conceding the point.

Also for some things like ice cream not being cold, you get explore the idea with them. Cold is, in fact, not a thing, it is just a lack of heat.