Eddie Brock would try to expose Tony, not prop him
Eddie Brock seems to have a strong sense of doing what's right. He's also an investigative journalist. So it seems WAY more likely that Eddie would try to bring Tony's crimes to light, not attack Team Cap. The person who suggested this thinks that Eddie would also seriously consider letting Venom eat Tony (if the investigation revealed enough horrible actions). Or Eddie may prefer to leave him alive to witness his crimes being exposed and his reputation ruined.
Note: I haven't seen the film, so Eddie and Venom may be out of character.
***
Once Eddie started digging into the actions of Tony Stark, the hole just got deeper and deeper.
He'd always had the idea of a report on Stark in the back of his mind, but other, more obvious criminals came first.
With Stark being the face of the Sokovia Accords, he went to #1 on Eddie's investigation list.
He'd sort of hoped that Stark was on the level. Of course, the decades of negligence before Stark became Iron Man were awful, but supposedly Stark turned over a new leaf.
Turned out it was more the leopard didn't change his spots, he just paid for a paint job.
Eddie had found cover-up after cover-up, from Stark shooting weapons into a crowd while drunk, to creating the Ultron AI that destroyed Sokovia, to some seriously shady recruiting of the poor kid who was Spider-Man, to breaking the Sokovia Accords.
It was watching footage of Stark cutting off a man's arm and then shooting him in the back that brought Venom out.
Venom thought, "I could eat him for you." Venom's tongue was already wiggling in anticipation.
Eddie said, "No..." But it wasn't very forceful. Eddie was now on a site created by ex-Stark Industries employees. None of them had anything good to say about their former boss.
Venom thought, "Are you sure? No more abusssssing hissss power or hiding hissss crimesssss."
Eddie thought about how Stark said one thing and did another. And used his money and power so he always looked good.
He shook his head and said, "No. I think the world deserves to see Tony Stark as he really is. And Tony Stark needs to see that happen."
***
Eddie sat back and watched the news feeds pick up the evidence that he'd provided. He was glad he'd decided to leave Spider-Man out of it--the kid didn't need the publicity.
He smiled as he watched Stark try to weasel his way out of responsibility and fail. For a man who preached accountability and consequences, Stark didn't seem to like them much.
Venom thought, "You were right. Thissss issss better. But I am sssstill hungry. Maybe I can eat him later."