Answer
The two aspects of Wegener’s continental drift hypothesis that were objectionable to most Earth scientists are that his theory of continental drift was not supported by any mechanism and that he proposed that "larger and sturdier continents" broke through the oceanic crust somehow, despite no evidence that this could happen on the oceanic floor.
Work Step by Step
His hypothesis contradicted the prevailing view of the time that the continents were stationary. Also, his hypothesis did not rest on any evidence. He only suggested the tides were somehow responsible.
See p. 43 of text for more details and some cool pictures.
