"As FO I would continue running checklists and executing the duties required for safe operation of the aircraft. After the flight I would clarify the captain's expectations for the future and state that I had misunderstood his intent on employing anti-icing."

if they ask if the captain was being unreasonable-

"Turing the icing off and then back on again was probably somewhat obnoxious, but there's no benefit to escalating the situation and damaging CRM. I've flown with obnoxious captains/aircraft commanders before, and I'm sure I'll do it again. My priority here is to maintain my own professionalism."