One of the most annoying things that I get from wap purists is the "Believe it is so annoying" when they have no problem with "Ttebayo".
Yes, ttebayo doesn't have a meaning. However, in context, neither does "Believe it!"
I mean, think about the word "well", it can mean the adverb of good, it can mean 'not ill' or it can be an interjection. In the context of an interjection, well has no meaning, just like "Believe it!" has no meaning when Naruto actually uses the phrase.
Another thing is that people seem to forget that Naruto is supposed to be annoying. He says 'ttebayo' in a manner that's annoying most of the time. The dubbers would be doing their job incorrectly if they left out any annoying sentence ending phrase.