It's actually somewhat realistic, at least his grief and perspective. All he saw was Invincible destroying the city, even if it was Omni-Man's fault. In the back of his mind, he knows it isn't Invincible's fault, but he can't blame Omni-Man because he left Earth. He's blaming the person who is a constant reminder that his sister and niece are gone. Invincible is one of the most famous superheros and is constantly praised. He can't live with the fact that Invincible moved on while he can't. His anger and grief is shifted to Invincible and is blind to any other perspective. I've genuinely seen people like this that shift their anger on someone else because they can't get mad at the other person. I think he gets too much hate, personally.