The Malian international's dismissal was his second since joining the Hoops from Ligue 1 side Nancy in January 2012 and arguably cost Rangers a potential draw.
Despite Hughes thinking that Monday's red card was harsh, he has confessed that Diakite has to be shrewder in the tackle in future.
"I think it's a little bit harsh on Samba Diakite. It was disappointing because he's made two fouls," said Hughes.
"I thought the first one, he's making a genuine attempt to cut the ball out and unfortunately the lad has just nipped it away from him. It's a foul, is it worthy of a booking? You can debate it. The second one, he's got an eye on the ball and the lad has come in from the side. I'm not sure he even knew he was there.
"Unfortunately he's had a number of those challenges and he seems to get penalised very readily. It's something he's obviously going to have to work on."
The result leaves QPR bottom of the Premier League table and winless after six matches.