From wikipedia
"Drinking the Kool-Aid" is a phrase that became known because of the 1978 Jonestown Massacre. It suggests that one has mindlessly adopted the dogma of a group or leader without fully understanding the ramifications or implications. At Jonestown, Jim Jones' followers followed him to the end: after visiting Congressman Leo Ryan was shot at the airstrip, all the Peoples Temple members drank from a metal vat containing a mixture of "Kool Aid", cyanide, and prescription drugs Valium, Phenergan, and chloral hydrate.
Harry telling me to keep drinking the kool-aid when it comes to Trump just gave me a good chuckle