No, it can't. "Ranting" is clearly some sort of verb rather than some sort of noun.
The kind of analysis that you and I were taught at school has trouble with such sentences. The modern way of approaching such questions in universal grammar (check it out) makes use of noun phrases (NPs) and verb phrases (VPs). These things probably have formal definitions at the academic level, but for me it is sufficient to think that NPs are phrases that do nouny things and VPs are phrases that do verby things.
I would say that "keeps ranting about" is a VP. It could just as well be "won't stop ranting about", "continues to rant about", "never ceases to rant about" etc. They are all VPs. And the rest of the sentence that follows is an NP, and the object of the VP.
Of course both the VP and the following NP can be further analyzed in finer detail. I hasten to add that I'm no expert, and am just trying to provide the barest introduction.
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