Based on what I am reading here, I don't see anywhere that KIA Corporate is trying to deceive customers. The documentation clearly states that the 18" wheel option lowers the top speed. This misinformation came from the dealership, specifically a salesperson(s) who clearly does not know the facts about the vehicle. I'm sure as enthusiasts most of us know more about these vehicles than a lot of the folks selling them. As said multiple times, you can work with your dealer or reach out to KIA corporate to see if they can assist. As humans, we understand that mistakes get made, the key is how you handle things when this occurs. Let's hope this can get resolved.
Going on a mission to disparage an entire company based on information from a salesperson that doesn't know his product seems like overkill. For that, you should have a nice chat with the General Manager of the dealership to work out something. I've had bad experience with sales folk, going to the top to express my dissatisfaction got results. Give that a shot, those folks have the power to do things your sales folk and their manager can't do. They car more about the business than your sales person does and want to ensure you have a good experience. Stop talking to the sale folk, look up who the GM is and reach out to them. Good luck.