When I was elected as a Union Steward, about 2 weeks after the election, my manager approached me and said if I would work with Management they would make things easy for me, if not, it was not going to be fun. It was the very first election that we had for being a Steward. My coworkers elected me because they knew I was honest and I would fight for them. Things did become tough. Some Stewards sell out, I refused to.
It was just the Manager and myself in the office. No veiled threat. Spoken word for word. No witnesses, so would have been "he said, she said". As Tom Petty said "don't back down".