Even if Theodosius claim would have been disputed during his day (which it wasn't), that wouldn't change the fact that the Empire we are talking about is the Roman Empire. He didn't claim to be the rightful heir to a once existing but now defunct Roman Empire, but he was the ruler (or one of the rulers) of that Empire. That's fact. You can stand on your head and scream "POV!" - it doesn't make any difference. The Byzantine Empire, as I have argued above, is the Roman Empire, at least until Justinian, based primarily on its eastern part but nonetheless.  

 Next time you will dispute the use of "United Kingdom of Great Britian", maybe because you dispute its unity or its greatness, or its Britishness (as British means Celtic) etc. In the case of a real dispute, Wiki gives the country's name as Republic of Macedonia and not as "Former Yugoslav Republic of Macedonia" or "state of Skopje".  

 Please get real and if you must post, please sign your posts.