Should George Zimmerman have been arrested?

yes. if the DA thinks she has enough to convict him than he should be arrested.

I don't know if he should have been arrested or not I don't know what the truth is but based on what has been revealed it would seem that it would be hard t o prove 2nd degree murder.

The arrest was probably for the best where Z is concerned. But when this does go to court, and as the trial progresses, and it looks like the DA may get their guilty verdict, the defense can make a plea bargain and try to get whats called "Imperfect self defense" which is allowed only in a limited number of jurisdictions in the US, Its when a person who acted in self defense with an honest but unreasonable belief that deadly force was necessary to do so could still be convicted of voluntary manslaughter or deliberate homicide committed without criminal malice. Since the DA is going for 2nd degree murder, that carries a life term in prison, and the imperfect self defense would carry 5 to 10 yrs. Or less. But I am unsure if FL has this type of plea bargain, MI does though. I do wonder how the Martin family would think of that. But hopefully if Z is found innocent, people will leave him alone and get on with their lives.