Striker Trevor Benjamin pulled a goal back for the ten man Robins.
"At 1-0 down we had a chance to get back into the game but that was the point when we had to keep things tight," said Onuora.
"But one goal became two and it escalated from there.
"There were two things we could do - face the challenge of rising to the occasion head on or suffer the kind of defeat we did.
"The players made a statement, which was that they didn't have enough about them to scrap and fight. There was nowhere to hide."