Is there any justification for a yellow card if…

I'd throw it under either careless or unsporting behaviour as @Sunny Jim puts it. Unsporting behaviour classed as a yellow card. Straightforward call for any ref really.

Found it amusing that Robbie Savage tried to defend it, no doubt as the sort of shit-house tactic he was regularly guilty of during his career.
 
If it's deliberate yes, under unsporting behavior, pretty simple decision.
How? The ball is still in play? Players deliberately play the ball off others in every game.
It’s a ridiculous decision. You can never have a shot on goal ever again!
 
There is no law against booting the ball when the game is live. For me that's the worst yellow I have ever seen simply because there is no law against booting the ball. I don't care if it was unsportsmanlike or even dangerous. If there is no rule broken you cant give a yellow. Its ridiculous. The ref can't just make sht up.
I’ve always thought football should have a catch-all rule like cricket where basically being a dick can be punished, regardless of what the rules say.

I’d have booked Bruno. Cos he was being a dick.
 
How? The ball is still in play? Players deliberately play the ball off others in every game.
It’s a ridiculous decision. You can never have a shot on goal ever again!

Kicking the ball against a downed opponent deliberately is unsporting behaviors and an obvious yellow. The key point here is deliberately kicking it in to the opponent as a malicious act, as opposed to shooting at goal, playing a long pass etc and it coincidently hitting another player.

Obviously if it's not deliberate, it's not a yellow.

That judgement is for the referee. Unsporting behavior is a catch all, it's in the laws. Like dissent, you don't see it enforced properly. It would be great it dissent was actually enforced properly. Players whining at the ref continually ruins the spectacle and none of the refs have the stones to yellow for it when they should.