They are mocking the fact that those soldiers ended up at the airport.
It's along the lines of, "You were told the airport is yours, weren't you? But when you rolled up here, who was here? Donetsk Republic's army that's who!"
"They sent you here like cannon fodder."
Motorola: "Why did you lead your men into a slaughter commander? You are being told the airport is under your control. Well, you're in the airport now."
Later the guy says that the shell has been opened and modified and that they'll find out what was done to it. I think he is implying something might have been put in there to cause more collateral harm or something... I'm very dubious on the idea making a factory built deadly munition deadlier by hand.
It appears someone messed up bad and they ended up easy picking for the rebels. Or at least so the rebels say.