Boyd was outstanding throughout for Posh, and Ferguson was in no doubt he was unfairly challenged by Adam Virgo in the incident which led to Keates' 65th-minute penalty.
He said: "Boyd was fouled for the penalty. The Brighton defender left his leg in and there wasn't much doubt about it. Boyd is a very talented individual and simply wants to get on the ball and play."
Posh had lost their previous two away games and Ferguson stressed the importance of picking up points on their travels.
He added: "Our home form is solid but we need more points away from home and we've got to maintain a good togetherness in the team."