Wall's words are pretty obvious here. Unhappy with Thompson fouling him hard twice, he comes over to him and shouts, "Go to the basket next time, and I'll knock your a** out." That alone probably wouldn't have caused him to be ejected, but when Thompson didn't respond, he shouted "GO TO THE BASKET" four more times. That gave him the ax.
Afterwards, Wall took responsibility for his actions.
"The way I got hit those first two times, I felt like I would state my point and say something, and I guess they gave me a technical," Wall said, via Monumental Network. Later, while answering a question about the team's road trip as a whole, Wall said he "let the team down by getting ejected" in this game.
Thompson's response, via Marcus Thompson of the Contra Coast Times:
"I think he was just frustrated. I didn't think it was that big of a deal, though. I know John. I've played with him. In that moment, I understand. You're frustrated. After you get fouled hard, then the next play you think you get fouled hard again. He's competitive. He let his emotions get the best of them."
"I would've been unhappy, too. But I'm not trying to get kicked out. It is what it is."