He was right, romaji is just something "we" have come up with, and its actual use is extremely limited. Chinese characters, on the other hand, were basically implemented into Japanese in order to be able to make a writing system - and thus was a part of it "all along". If not, then at least for a fricking long time.
I agree, romaji should be counted as
a writing system, but not in a way that makes it seem more important than it is.