In the context of the increasing evidence of Russian involvement in our elections and reports about their support of our enemies (http://www.foxnews.com/world/2017/05/17/evidence-russian-mil... or https://www.washingtonpost.com/news/checkpoint/wp/2017/04/24...) I'm not sure it's baseless fear mongering.
Greenwald isn't exactly an impartial source when it comes to Russia either - he has his own overt biases. It's healthy to be skeptical but naive to assume Russia is a benevolent actor on the world stage (even more so in the context of events like https://en.m.wikipedia.org/wiki/Malaysia_Airlines_Flight_17).