Conservative and some liberal students at New York University were dismayed last week after school officials, citing security concerns, canceled an event headlining controversial blogger Milo Yiannopoulos.

Mr. Yiannopoulos, the tech editor of the Breitbart website, has been criticized for his comments on Muslims, Black Lives Matter activists and feminists. Twitter Inc. banned Mr. Yiannopoulos in July for a series of tweets directed at actress-comedian Leslie Jones.

In...