I do not think that there should be debated in the United States of America done in anything other than English. I do not think that people should engaged in debates unless it is in English. Doing a debate in a foreign language would be causing a lot of problems for other Americans.
Keeping it in English will allow all debaters on this website to listen and communicate with each other. Major points of the argument will not be brought up so many times, because the people communicating will read each others opinions and see what they should or should not say to keep things interesting. There can be a separate section of the website for debates in French, German, Italian, etc. but for now, the language should be English to allow for global communication without repetitiveness.
I do not believe debates in languages other than English should be disallowed. There are many languages used on this planet and for those that speak these other languages, it would be unfair to say they couldn't debate. Debate can take many forms and involve varying numbers of people. Debate is a normal part of any society.
I think the major debates in this country should be in English since it is the language of our country. However I don't see a need to disallow people from debating in another language. There are some freedoms in this country that should not be taken away. We should be allowed to talk in any language we choose.
There's no reason debates in other languages shouldn't be allowed. Americans especially seem to have a problem with learning other languages, although people across the world bend over backwards to conform to their needs. Instead of not allowing debates in other languages, maybe you could take the time and effort to learn a new language like those who aren't native English speakers did?
To not allow debates in other languages is wrong. I don't think the other languages should be used with the English debates though. There should be a section where you choose the language and see all debates in that language and must follow the language you have chosen when you respond.