"The referee is the man who calls it. He deemed it a sending-off and we'll live with that," Williamson said after the game at Home Park.
"Maybe the referee has got it right, so I am not going to put him in an embarrassing position by appealing. That'll be an end to it.
"It was a fantastic result today. I felt we worked hard, from the first minute to the last. I'm pleased for everybody.
"The players worked their socks off, the fans got behind us, and I'm delighted they got their rewards."