"Water (to cool) will damage the barrel"

R.o. at hot wells range sees me trying to examine my barrel for leading. I'd gotten it too hot to hold and i was looking for a rag or something to protect my fingers and I see their water fountain. He tells me it will screw up my barrel. I need to let it air cool
The guys got a race gun and 2 spare mags. I guess he's expecting jihadis
Edit: it looked like it had lead at the Range. I got home and sprayed some rem
oil in and a couple passes with the plastic brush and it's clean as a...

"Water (to cool) will damage the barrel"