I agree with you on some respects here. For example, if she started it and hit him, and he violently shoved her to the ground and it knocked her unconscious, yes... even if legally self-defense, I would roast him with you. He's an NFL DT and she's a small woman, after all.
However, the release states that she did not have any significant injuries and they had no reason to believe that he applied any real force back on her. The release also states that a neutral party was able to confirm his story. At no point was she knocked unconscious by Brantley nor did he punch her/knock out a tooth. So although he has plenty of character concerns, if he simply pushed her back/shielded her off without any significant/violent force, it seems like an understandable move.