Dissidents like Eugene V. Debs were very negatively impacted by World War I. The wave of patriotism that swept the country during the war led to a great deal of intolerance of people who held attitudes that were at all different from those of the majority.
During WWI, the US government launched a big push to promote patriotism and discourage dissent. For example, the Sedition Act of 1918 made it illegal to use "disloyal" language when talking about the government, the flag, or the armed forces. Debs himself was sentenced to 10 years in prison for violating this law by opposing the draft. Hundreds of other dissidents were charged under this law as well.
In this way, WWI had a very negative impact on dissidents.