Victorious's debating style is very poor to say the least. If he cannot counter what someone is saying than he will try and ask for very specific details -that are never actually involved within the story, if it doesn't coincide with his beliefs, he will make up principals that go against what the characters tell us as a means to try and stalemate the person he's debating with. He also enjoys trying to create paradoxes. Once he believes that he has achieved this, he will determine that his theory is as valuable and holds as much weight as their own. For example:
a) Goku states that to perform fusion, characters need to be fairly close in power, but he also states that he's never tested it out because nobody was on par with him.
The conclusion here is that the powers need to be close, or on par with one another in order to perform fusion. Dende is sitting right there and knows about fusion. He doesn't contradict this statement. So it's a fact.
Whereas Victorious will argue:
b) Goku didn't try it out so that means he can suppress himself and still do fusion.
Well... this goes against what Goku said originally, and it goes against EVERYTHING we're told in the story. That characters need to be fairly close in power to even consider fusion.
At this point, it's a forgone conclusion that he's lost this debate.