On reflection, the analogy bites a little closer than I might like to admit. They are stalkers, to each and every one of us. What they do is literally an attack on the entire internet (- IAB).
Please bear in mind that GCHQ are actually worse than the NSA in every way. They have essentially no "equities issue" to speak of; they operate both internationally and domestically; they have repeatedly ignored the law with essentially zero oversight, consequences or meaningful reproach; they have spied, and continue to spy, even on UK Government departments and MPs; and they are very probably about to get official powers to do mass hacking, which in typical form, they've already been doing for years anyway.
Bear in mind also that this is software that they use for analysis of data collected by spying on all of us; graph analysis software that is literally being used right now to select who to murder.
Forgive me if, therefore, I might hesitate to run any of the code of an organisation with a long history of deploying malware against innocent people.