If Martin had been afraid for his safety he could have simply go into his house. There was more than enough time. If Zimmerman had assaulted martin first he managed to do so ineffectively that he didn't leave a mark on him. The physical evidence and the only eyewitness to actually see the fight show Martin beating on Zimmerman while the only injuries to Martin where scraped knuckles and a gun shot wound. The rest is just made up narrative of people "know" happened based on their own personal bias and prejudiced. Just like the argument that we know Martin was profiled. Only evidence? He was black and lets not forget it happened in the south. Sounds like a clear cut case of racial bias and bigotry just got twisted in 180 is all.
If Zimmerman had not had a gun and he would not have shot Martin it would have been a pretty simple case to convict martin of assault. If Martin had not been black the case never would have went to court.