No shit he flew off the handle. He's just had to arrest a bunch of his friends, had his arguably best friend severely injured, if he survives (didn't yet know at that time), the avengers, which tony has been detected facto leader and funder for since shield collapsed, are functionally gone because of caps decision to go rogue taking many of them with him, and tony is currently putting himself at serious risk of joining the others in that jail for trying to help cap out. Not to mention the whole airport thing was Tony's last ditch attempt to stop them just putting out a kill order on caps half of the avengers in the first place.
His reward for all that is finding out cap didn't trust him at all after all, which lead to him finding out cap trusted his parents murderer to the point where he wouldn't even tell tony about it, so that tony found out at the worst possible time.
The film might as well have been Captain America: tony had enough big fuck ups in the MCU , I want my turn.