Not correct.
What happens during a natural disaster? Doesn’t the governor of the state activate them?
There is no Governor of Wdc.
Yes, Governors can activate their own state NG. I believe the poster was referring to the DC NG which the President can only activate. However, I read he has delegated such authority to Sec. of Defense, and he as delegated it to the Sec. of Army. The Mayor's request for DC NG has been approved, so they'll be there.
I wouldn't be concerned since they will probably just play crowd/traffic cops and escorts for arrestees to off site. I doubt they will be armed and will just mill around in the background. The ones to worry about are the DC Police.
I do not believe there is a Governor of Washington DC.
IMHO