De Man's point is a question is both rhetorical and grammatical, and the one cannot be reduced to the other. Both readings are available.

德曼想指出的是，一个问句既是修辞型问句又是语法型问句，那么一个不能变成另一个，两种理解都有效。

耶鲁公开课 - 文学理论导论课程节选