It's a quite simple idea; for someone to be part of a debate, they need to be taught well enough to think in a more complex manner, and then carry out those ideas properly. Though anyone can get into an argument, debates , in my opinion, are arguments that are based not only on opinion but fact. If someone is intellectually superior, they can follow that criteria, and if they are not, they will lack the proper skills to carry on a debate. Now, does someone have to be Einstein to partake in a debate? No. But a good agree of intelligence is still very much required.
No, unfortunately, debating does not require intelligence. For a decent debate, both sides should know a little bit about the material they will be speaking about, but overall the most important aspect of debating is the opinion one holds. Without an opinion, you don't know what side you stand on, but even if you have developed a misinformed opinion, you could still attempt to debate based on that opinion.