I don't think there should be a common language in the EU - the variety of languages is something I enjoy when travelling to different places and it'd be a shame to ruin this.
You seem to think: Now no language is common and SvobodaGab wants to impose some. However, it's not true. We already have a common language, called English. People simply tend to have some common language. However, I want the common language to be better than it is today. That's why I propose Esperanto - it belongs to no nation and that's why it wouldn't ruin the variety of national languages (which you want to enjoy and so do I) as much as English today already does.