Yes, I disagree. Why does/did RSA require a patent?

Require is the wrong word. The question is were we better off with or without them having a patent. Not keeping RSA a trade secret seems like a win for society.

That presupposes a lot. Who says it would have been kept a "trade secret"? And, supposing it would have been, who's to say someone else wouldn't have come along with an alternative open solution?