What is the definition of a doomsday cult?
You can find various definitions on the internet. Here is one of them:
"A doomsday cult is a new religious movement or cult that says that the world is about to end. According to these cults, there will be a catastrophe." (SimpleEnglishWikipedia)
If you go by this definition, my first serious indoctrination with a doomsday cult was in middle school (I was not a Jehovah's Witness until later in life - at present I am disfellowshipped and banned from attending locally). I joined "Future Problem Solvers", an after school club with members gleaned from science classes who were told they had to be the active next generation that would takeover the affairs of the world and learn how to solve problems created by hundreds of years of selfishness. Additionally, the "science" classes told that someday the sun was going to explode and burn the earth with fire, unless a meteorite hit first and caused mass death, or a nuclear catastrophe.
I was terrified as a young person because of these stories told by evolutionary atheists.
You can say what you want about the WTBT$. They do a lot of really bad things and bring reproach on God's Name, and I do not support their heinous activities or false doctrines. But I don't think that pointing the finger with the accusation "You're a doomsday cult!" is either productive or accurate. They are a cult in different ways, but the "doomsday" thing isn't the right adjective. At the end of the day, Jehovah's Witnesses recognize that God will preserve the earth and some of humankind, which is a lot more than the evolutionary atheists are willing to acknowledge. Evolutionary atheists teach that the entire earth will be destroyed and all life on it.
The borg is not accurate about all the ways God will handle things - the borg makes distinctions that are not accurate according to the Bible and the way we see God's personality reflected in His Son, Christ Jesus. But the Bible itself is not "doomsday" to the degree evolutionary atheism is "doomsday".
I can understand that when people have been hurt by the borg they have wild talk and all - I've done my share - and I am confident Jehovah will set things straight and expose all the heinous things religious hypocrites in the borg are guilty of. But I think there are better "insults", if you will, than the "doomsday cult" thing, unless the evolutionary atheists want to be accused of "the pot calling the kettle black." Just saying.