Despite not playing for the last 19 days due to a coronavirus outbreak in their camp, Villa kept Manchester City at bay for 79 minutes until Bernardo Silva controversially broke their resilience.
Rodri came from on offside position to dispossess Tyrone Mings of the ball before setting up Silva, whose left foot strike beat Emiliano Martinez in the Villa goal for the game’s opener.
Smith was incensed that the goal was allowed to stand and was sent off by referee Jon Moss for going too far with his protests before Ilkay Gundogan made sure of the points for City with a late penalty.
"I still don't understand the rule if I’m honest," said Smith after the game.
"I don't think anyone can tell me why a goal has been given. He [Rodri] has taken advantage of an offside position. He comes back and tackles Tyrone Mings from behind.
"What was Tyrone supposed to do, just let it go through? He was 10 metres offside. Do you just stand there all the time now?
"I thought they'd at least go over to the screen as it looked clear offside. I looked at the screen myself and it looked like a clear offside.
"When I realised they weren't even going to take a look I told the fourth official I thought they had got juggling balls for Christmas.
"If that's the law then definitely [it should be changed]. He's standing offside and taking an unfair advantage from that. Nobody in this stadium thinks that goal should have stood, so you can't tell me it should have stood and that tells you there is a fault with the law."
He added: "I don't think anyone can tell me why it's been given. What is Tyrone meant to do? Can you stand 10 yards offside now?
"Nobody in the stadium feels that should have counted so you can't tell me that should have counted."