George Norris is opposing the idea of US entry into WWI on two major grounds.
First, he is saying that the US was never truly neutral. He is saying that Wilson is proposing to enter the war on Britain's side even though Britain violated international law just as Germany did. He says
No close student of recent history will deny that both Great Britain and Germany have, on numerous occasions since the beginning of the war, flagrantly violated in the most serious manner the rights of neutral vessels and neutral nations under existing international law, as recognized up to the beginning of this war by the civilized world.
He sees this as proof that Wilson's administration was taking sides in the war rather than truly remaining neutral.
Second, Norris is alleging that the country is being pushed into war for the financial benefit of certain groups of people. He thinks that the war helps the rich financiers who are going to be selling weapons and other such things to the government. He argues that
War brings prosperity to the stock gambler on Wall Street--to those who are already in possession of more wealth than can be realized or enjoyed.
Norris, then, is saying that the US was not truly neutral in the war and that it should have taken more care to truly stay neutral. In addition, he argues that the war is going to help the rich to get richer while the poor have to go and fight.