Like I mentioned before, my argument is moot due to the simple fact that kana should be learned immediately regardless, BUT, for other reasons than what you guys are stating.
I stand by my point that romaji in itself DOES NOT corrupt speech. It is not difficult to view roman characters in a different light depending on the language they are being applied to, in fact, bilingual people have been doing this easily for hundreds of years when switching from English to French, German, or Spanish. In each language, the roman alphabet is interpreted in different ways, but most people have no problem understanding that the English "J" is different from the Spanish "J".
I also believe there is a valid reason why most Japanese instruction begins with romaji. It allows the learner to get a head start on understanding things like syntax and grammar before memorizing the kana.
In all honesty, I think the argument that romaji must be abandoned to correctly pronounce Japanese is like saying all hiragana must be abandoned if it has a kanji equivalent. They are ALL mere symbols, and can all mean the same thing depending on context, but which is easier to learn, the 26 character alphabet you were raised with, the 46 hiragana and katakana, or the thousands of Chinese characters?