Interesting Times

Why did several New York City politicians come out of the woodwork to boycott, divest, and sanction the "free expression of contrary ideas" and "reasonable debate without censorship"?

You'd have to ask them. Perhaps free expression of contrary ideas and reasonable debate without censorship is against their belief systems. Perhaps some people are more free than others, depending upon who gets paid and how much. Perhaps freedom isn't free and it isn't for everyone.
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Nut jobs, desperately living in their "look at me! look at me!" universe, gravitated toward political thievery as career choices. They became more and more outrageous in their speech and their antipersonnel anticivilian alliances as the pols were regarded with less and less liking or respect. It was a proportional ratio of opposites. Maybe we live in interesting times.