It was easy to understand why this looked so petty. Wahh, he stole my powers and won't give them back. No, this wasn't about name-calling or hurt feelings. This wasn't tattling to the teacher or spreading a mean rumor out on recess. To Sabo, this matter cut so much more deeply than anyone could understand from a single glimpse, and there was no way he could knock anything off, except perhaps for the look on Gambit's grumpy face. If Sabo didn't vent this, HE would be the next thing to explode.
"Then how did you get them!?" he bellowed, his booming voice actually causing the ground to quake gently. He was so consumed, so blindly furious that he aimed his open palms at Gambit. Not understanding them in the least, he gestured at the cajun several times, trying to turn these strange new powers on him. Make him explode. Naturally, nothing at all came of it, which only frustrated Sabo even more, and he grunted frantically.
The burning anger he felt was kindled by pain, both mental and physical. Having those powers taken away was actually hurting him, like needles beneath his skin, keeping him from thinking straight or dealing with Gambit like the friend he really was. But it wasn't because the transfer itself hurt, or because he felt some petty resentment - it was because those powers were a keepsake from someone else, and this was a very sensitive subject.
"Those aren't your's! They're Ace's!" Sabo shouted, glaring sharply at Gambit. Very much like a childish squabble, he stomped one foot down on the ground, causing the pavement to crack under his heel.
Ace, his brother and the previous wielder of those fiery powers, had been killed while Sabo, oblivious and lost in amnesia, did nothing to help. Learning of his death and suddenly regaining all of his memories had literally shocked Sabo so badly that he had screamed and wailed in anguish for hours, then passed out for three days straight. He had later struggled furiously to gain those powers for himself, refusing to allow anyone else to tarnish Ace's memory. Now, he had been helpless to prevent those powers from being taken away. He was caught in his feelings of weakness and regret, and his unresolved emotions were visibly pushing him towards the brink of tears.
"...you can't have them..." he gasped, breathing more feverishly now. He didn't want to hurt Gambit, but the rage he felt stirred up so much conflict that it was straining him physically. "Please...just give them back."